Table Of Contents


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What’s New

These are new features and improvements of note in each release.

v0.17.1 (November 21, 2015)


We are proud to announce that pandas has become a sponsored project of the (NUMFocus organization). This will help ensure the success of development of pandas as a world-class open-source project.

This is a minor bug-fix release from 0.17.0 and includes a large number of bug fixes along several new features, enhancements, and performance improvements. We recommend that all users upgrade to this version.

Highlights include:

  • Support for Conditional HTML Formatting, see here
  • Releasing the GIL on the csv reader & other ops, see here
  • Fixed regression in DataFrame.drop_duplicates from 0.16.2, causing incorrect results on integer values (GH11376)

New features

Conditional HTML Formatting


This is a new feature and is under active development. We’ll be adding features an possibly making breaking changes in future releases. Feedback is welcome.

We’ve added experimental support for conditional HTML formatting: the visual styling of a DataFrame based on the data. The styling is accomplished with HTML and CSS. Acesses the styler class with the, attribute, an instance of Styler with your data attached.

Here’s a quick example:

In [1]: np.random.seed(123)

In [2]: df = DataFrame(np.random.randn(10, 5), columns=list('abcde'))

In [3]: html ='viridis', low=.5)

We can render the HTML to get the following table.

a b c d e
0 -1.085631 0.997345 0.282978 -1.506295 -0.5786
1 1.651437 -2.426679 -0.428913 1.265936 -0.86674
2 -0.678886 -0.094709 1.49139 -0.638902 -0.443982
3 -0.434351 2.20593 2.186786 1.004054 0.386186
4 0.737369 1.490732 -0.935834 1.175829 -1.253881
5 -0.637752 0.907105 -1.428681 -0.140069 -0.861755
6 -0.255619 -2.798589 -1.771533 -0.699877 0.927462
7 -0.173636 0.002846 0.688223 -0.879536 0.283627
8 -0.805367 -1.727669 -0.3909 0.573806 0.338589
9 -0.01183 2.392365 0.412912 0.978736 2.238143

Styler interacts nicely with the Jupyter Notebook. See the documentation for more.


  • DatetimeIndex now supports conversion to strings with astype(str) (GH10442)

  • Support for compression (gzip/bz2) in pandas.DataFrame.to_csv() (GH7615)

  • pd.read_* functions can now also accept pathlib.Path, or py._path.local.LocalPath objects for the filepath_or_buffer argument. (GH11033) - The DataFrame and Series functions .to_csv(), .to_html() and .to_latex() can now handle paths beginning with tildes (e.g. ~/Documents/) (GH11438)

  • DataFrame now uses the fields of a namedtuple as columns, if columns are not supplied (GH11181)

  • DataFrame.itertuples() now returns namedtuple objects, when possible. (GH11269, GH11625)

  • Added axvlines_kwds to parallel coordinates plot (GH10709)

  • Option to .info() and .memory_usage() to provide for deep introspection of memory consumption. Note that this can be expensive to compute and therefore is an optional parameter. (GH11595)

    In [4]: df = DataFrame({'A' : ['foo']*1000})
    In [5]: df['B'] = df['A'].astype('category')
    # shows the '+' as we have object dtypes
    In [6]:
    <class 'pandas.core.frame.DataFrame'>
    Int64Index: 1000 entries, 0 to 999
    Data columns (total 2 columns):
    A    1000 non-null object
    B    1000 non-null category
    dtypes: category(1), object(1)
    memory usage: 12.7+ KB
    # we have an accurate memory assessment (but can be expensive to compute this)
    In [7]:'deep')
    <class 'pandas.core.frame.DataFrame'>
    Int64Index: 1000 entries, 0 to 999
    Data columns (total 2 columns):
    A    1000 non-null object
    B    1000 non-null category
    dtypes: category(1), object(1)
    memory usage: 36.2 KB
  • Index now has a fillna method (GH10089)

    In [8]: pd.Index([1, np.nan, 3]).fillna(2)
    Out[8]: Float64Index([1.0, 2.0, 3.0], dtype='float64')
  • Series of type category now make .str.<...> and .dt.<...> accessor methods / properties available, if the categories are of that type. (GH10661)

    In [9]: s = pd.Series(list('aabb')).astype('category')
    In [10]: s
    0    a
    1    a
    2    b
    3    b
    dtype: category
    Categories (2, object): [a, b]
    In [11]: s.str.contains("a")
    0     True
    1     True
    2    False
    3    False
    dtype: bool
    In [12]: date = pd.Series(pd.date_range('1/1/2015', periods=5)).astype('category')
    In [13]: date
    0   2015-01-01
    1   2015-01-02
    2   2015-01-03
    3   2015-01-04
    4   2015-01-05
    dtype: category
    Categories (5, datetime64[ns]): [2015-01-01, 2015-01-02, 2015-01-03, 2015-01-04, 2015-01-05]
    In [14]:
    0    1
    1    2
    2    3
    3    4
    4    5
    dtype: int64
  • pivot_table now has a margins_name argument so you can use something other than the default of ‘All’ (GH3335)

  • Implement export of datetime64[ns, tz] dtypes with a fixed HDF5 store (GH11411)

  • Pretty printing sets (e.g. in DataFrame cells) now uses set literal syntax ({x, y}) instead of Legacy Python syntax (set([x, y])) (GH11215)

  • Improve the error message in when a streaming insert fails (GH11285) and when the DataFrame does not match the schema of the destination table (GH11359)

API changes

  • raise NotImplementedError in Index.shift for non-supported index types (GH8038)
  • min and max reductions on datetime64 and timedelta64 dtyped series now result in NaT and not nan (GH11245).
  • Indexing with a null key will raise a TypeError, instead of a ValueError (GH11356)
  • Series.ptp will now ignore missing values by default (GH11163)


  • The module which implements google-analytics support is deprecated and will be removed in a future version (GH11308)
  • Deprecate the engine keyword in .to_csv(), which will be removed in a future version (GH11274)

Performance Improvements

  • Checking monotonic-ness before sorting on an index (GH11080)
  • Series.dropna performance improvement when its dtype can’t contain NaN (GH11159)
  • Release the GIL on most datetime field operations (e.g. DatetimeIndex.year, Series.dt.year), normalization, and conversion to and from Period, DatetimeIndex.to_period and PeriodIndex.to_timestamp (GH11263)
  • Release the GIL on some rolling algos: rolling_median, rolling_mean, rolling_max, rolling_min, rolling_var, rolling_kurt, rolling_skew (GH11450)
  • Release the GIL when reading and parsing text files in read_csv, read_table (GH11272)
  • Improved performance of rolling_median (GH11450)
  • Improved performance of to_excel (GH11352)
  • Performance bug in repr of Categorical categories, which was rendering the strings before chopping them for display (GH11305)
  • Performance improvement in Categorical.remove_unused_categories, (GH11643).
  • Improved performance of Series constructor with no data and DatetimeIndex (GH11433)
  • Improved performance of shift, cumprod, and cumsum with groupby (GH4095)

Bug Fixes

  • SparseArray.__iter__() now does not cause PendingDeprecationWarning in Python 3.5 (GH11622)
  • Regression from 0.16.2 for output formatting of long floats/nan, restored in (GH11302)
  • Series.sort_index() now correctly handles the inplace option (GH11402)
  • Incorrectly distributed .c file in the build on PyPi when reading a csv of floats and passing na_values=<a scalar> would show an exception (GH11374)
  • Bug in .to_latex() output broken when the index has a name (GH10660)
  • Bug in HDFStore.append with strings whose encoded length exceded the max unencoded length (GH11234)
  • Bug in merging datetime64[ns, tz] dtypes (GH11405)
  • Bug in when comparing with a numpy scalar in a where clause (GH11283)
  • Bug in using DataFrame.ix with a multi-index indexer (GH11372)
  • Bug in date_range with ambigous endpoints (GH11626)
  • Prevent adding new attributes to the accessors .str, .dt and .cat. Retrieving such a value was not possible, so error out on setting it. (GH10673)
  • Bug in tz-conversions with an ambiguous time and .dt accessors (GH11295)
  • Bug in output formatting when using an index of ambiguous times (GH11619)
  • Bug in comparisons of Series vs list-likes (GH11339)
  • Bug in DataFrame.replace with a datetime64[ns, tz] and a non-compat to_replace (GH11326, GH11153)
  • Bug in isnull where numpy.datetime64('NaT') in a numpy.array was not determined to be null(GH11206)
  • Bug in list-like indexing with a mixed-integer Index (GH11320)
  • Bug in pivot_table with margins=True when indexes are of Categorical dtype (GH10993)
  • Bug in DataFrame.plot cannot use hex strings colors (GH10299)
  • Regression in DataFrame.drop_duplicates from 0.16.2, causing incorrect results on integer values (GH11376)
  • Bug in pd.eval where unary ops in a list error (GH11235)
  • Bug in squeeze() with zero length arrays (GH11230, GH8999)
  • Bug in describe() dropping column names for hierarchical indexes (GH11517)
  • Bug in DataFrame.pct_change() not propagating axis keyword on .fillna method (GH11150)
  • Bug in .to_csv() when a mix of integer and string column names are passed as the columns parameter (GH11637)
  • Bug in indexing with a range, (GH11652)
  • Bug in inference of numpy scalars and preserving dtype when setting columns (GH11638)
  • Bug in to_sql using unicode column names giving UnicodeEncodeError with (GH11431).
  • Fix regression in setting of xticks in plot (GH11529).
  • Bug in holiday.dates where observance rules could not be applied to holiday and doc enhancement (GH11477, GH11533)
  • Fix plotting issues when having plain Axes instances instead of SubplotAxes (GH11520, GH11556).
  • Bug in DataFrame.to_latex() produces an extra rule when header=False (GH7124)
  • Bug in df.groupby(...).apply(func) when a func returns a Series containing a new datetimelike column (GH11324)
  • Bug in pandas.json when file to load is big (GH11344)
  • Bugs in to_excel with duplicate columns (GH11007, GH10982, GH10970)
  • Fixed a bug that prevented the construction of an empty series of dtype datetime64[ns, tz] (GH11245).
  • Bug in read_excel with multi-index containing integers (GH11317)
  • Bug in to_excel with openpyxl 2.2+ and merging (GH11408)
  • Bug in DataFrame.to_dict() produces a np.datetime64 object instead of Timestamp when only datetime is present in data (GH11327)
  • Bug in DataFrame.corr() raises exception when computes Kendall correlation for DataFrames with boolean and not boolean columns (GH11560)
  • Bug in the link-time error caused by C inline functions on FreeBSD 10+ (with clang) (GH10510)
  • Bug in DataFrame.to_csv in passing through arguments for formatting MultiIndexes, including date_format (GH7791)
  • Bug in DataFrame.join() with how='right' producing a TypeError (GH11519)
  • Bug in Series.quantile with empty list results has Index with object dtype (GH11588)
  • Bug in pd.merge results in empty Int64Index rather than Index(dtype=object) when the merge result is empty (GH11588)
  • Bug in Categorical.remove_unused_categories when having NaN values (GH11599)
  • Bug in DataFrame.to_sparse() loses column names for MultiIndexes (GH11600)
  • Bug in DataFrame.round() with non-unique column index producing a Fatal Python error (GH11611)
  • Bug in DataFrame.round() with decimals being a non-unique indexed Series producing extra columns (GH11618)

v0.17.0 (October 9, 2015)

This is a major release from 0.16.2 and includes a small number of API changes, several new features, enhancements, and performance improvements along with a large number of bug fixes. We recommend that all users upgrade to this version.


pandas >= 0.17.0 will no longer support compatibility with Python version 3.2 (GH9118)


The package is deprecated and will be replaced by the pandas-datareader package. This will allow the data modules to be independently updated to your pandas installation. The API for pandas-datareader v0.1.1 is exactly the same as in pandas v0.17.0 (GH8961, GH10861).

After installing pandas-datareader, you can easily change your imports:

from import data, wb


from pandas_datareader import data, wb

Highlights include:

  • Release the Global Interpreter Lock (GIL) on some cython operations, see here
  • Plotting methods are now available as attributes of the .plot accessor, see here
  • The sorting API has been revamped to remove some long-time inconsistencies, see here
  • Support for a datetime64[ns] with timezones as a first-class dtype, see here
  • The default for to_datetime will now be to raise when presented with unparseable formats, previously this would return the original input. Also, date parse functions now return consistent results. See here
  • The default for dropna in HDFStore has changed to False, to store by default all rows even if they are all NaN, see here
  • Datetime accessor (dt) now supports Series.dt.strftime to generate formatted strings for datetime-likes, and Series.dt.total_seconds to generate each duration of the timedelta in seconds. See here
  • Period and PeriodIndex can handle multiplied freq like 3D, which corresponding to 3 days span. See here
  • Development installed versions of pandas will now have PEP440 compliant version strings (GH9518)
  • Development support for benchmarking with the Air Speed Velocity library (GH8361)
  • Support for reading SAS xport files, see here
  • Documentation comparing SAS to pandas, see here
  • Removal of the automatic TimeSeries broadcasting, deprecated since 0.8.0, see here
  • Display format with plain text can optionally align with Unicode East Asian Width, see here
  • Compatibility with Python 3.5 (GH11097)
  • Compatibility with matplotlib 1.5.0 (GH11111)

Check the API Changes and deprecations before updating.

New features

Datetime with TZ

We are adding an implementation that natively supports datetime with timezones. A Series or a DataFrame column previously could be assigned a datetime with timezones, and would work as an object dtype. This had performance issues with a large number rows. See the docs for more details. (GH8260, GH10763, GH11034).

The new implementation allows for having a single-timezone across all rows, with operations in a performant manner.

In [1]: df = DataFrame({'A' : date_range('20130101',periods=3),
   ...:                 'B' : date_range('20130101',periods=3,tz='US/Eastern'),
   ...:                 'C' : date_range('20130101',periods=3,tz='CET')})

In [2]: df
           A                         B                         C
0 2013-01-01 2013-01-01 00:00:00-05:00 2013-01-01 00:00:00+01:00
1 2013-01-02 2013-01-02 00:00:00-05:00 2013-01-02 00:00:00+01:00
2 2013-01-03 2013-01-03 00:00:00-05:00 2013-01-03 00:00:00+01:00

In [3]: df.dtypes
A                datetime64[ns]
B    datetime64[ns, US/Eastern]
C           datetime64[ns, CET]
dtype: object
In [4]: df.B
0   2013-01-01 00:00:00-05:00
1   2013-01-02 00:00:00-05:00
2   2013-01-03 00:00:00-05:00
Name: B, dtype: datetime64[ns, US/Eastern]

In [5]: df.B.dt.tz_localize(None)
0   2013-01-01
1   2013-01-02
2   2013-01-03
Name: B, dtype: datetime64[ns]

This uses a new-dtype representation as well, that is very similar in look-and-feel to its numpy cousin datetime64[ns]

In [6]: df['B'].dtype
Out[6]: datetime64[ns, US/Eastern]

In [7]: type(df['B'].dtype)
Out[7]: pandas.core.dtypes.DatetimeTZDtype


There is a slightly different string repr for the underlying DatetimeIndex as a result of the dtype changes, but functionally these are the same.

Previous Behavior:

In [1]: pd.date_range('20130101',periods=3,tz='US/Eastern')
Out[1]: DatetimeIndex(['2013-01-01 00:00:00-05:00', '2013-01-02 00:00:00-05:00',
                       '2013-01-03 00:00:00-05:00'],
                      dtype='datetime64[ns]', freq='D', tz='US/Eastern')

In [2]: pd.date_range('20130101',periods=3,tz='US/Eastern').dtype
Out[2]: dtype('<M8[ns]')

New Behavior:

In [8]: pd.date_range('20130101',periods=3,tz='US/Eastern')
DatetimeIndex(['2013-01-01 00:00:00-05:00', '2013-01-02 00:00:00-05:00',
               '2013-01-03 00:00:00-05:00'],
              dtype='datetime64[ns, US/Eastern]', freq='D')

In [9]: pd.date_range('20130101',periods=3,tz='US/Eastern').dtype
Out[9]: datetime64[ns, US/Eastern]

Releasing the GIL

We are releasing the global-interpreter-lock (GIL) on some cython operations. This will allow other threads to run simultaneously during computation, potentially allowing performance improvements from multi-threading. Notably groupby, nsmallest, value_counts and some indexing operations benefit from this. (GH8882)

For example the groupby expression in the following code will have the GIL released during the factorization step, e.g. df.groupby('key') as well as the .sum() operation.

N = 1000000
ngroups = 10
df = DataFrame({'key' : np.random.randint(0,ngroups,size=N),
                'data' : np.random.randn(N) })

Releasing of the GIL could benefit an application that uses threads for user interactions (e.g. QT), or performing multi-threaded computations. A nice example of a library that can handle these types of computation-in-parallel is the dask library.

Plot submethods

The Series and DataFrame .plot() method allows for customizing plot types by supplying the kind keyword arguments. Unfortunately, many of these kinds of plots use different required and optional keyword arguments, which makes it difficult to discover what any given plot kind uses out of the dozens of possible arguments.

To alleviate this issue, we have added a new, optional plotting interface, which exposes each kind of plot as a method of the .plot attribute. Instead of writing series.plot(kind=<kind>, ...), you can now also use series.plot.<kind>(...):

In [10]: df = pd.DataFrame(np.random.rand(10, 2), columns=['a', 'b'])

In [11]:

As a result of this change, these methods are now all discoverable via tab-completion:

In [12]: df.plot.<TAB>
df.plot.area     df.plot.barh     df.plot.density  df.plot.hist     df.plot.line     df.plot.scatter      df.plot.hexbin   df.plot.kde      df.plot.pie

Each method signature only includes relevant arguments. Currently, these are limited to required arguments, but in the future these will include optional arguments, as well. For an overview, see the new Plotting API documentation.

Additional methods for dt accessor


We are now supporting a Series.dt.strftime method for datetime-likes to generate a formatted string (GH10110). Examples:

# DatetimeIndex
In [13]: s = pd.Series(pd.date_range('20130101', periods=4))

In [14]: s
0   2013-01-01
1   2013-01-02
2   2013-01-03
3   2013-01-04
dtype: datetime64[ns]

In [15]: s.dt.strftime('%Y/%m/%d')
0    2013/01/01
1    2013/01/02
2    2013/01/03
3    2013/01/04
dtype: object
# PeriodIndex
In [16]: s = pd.Series(pd.period_range('20130101', periods=4))

In [17]: s
0   2013-01-01
1   2013-01-02
2   2013-01-03
3   2013-01-04
dtype: object

In [18]: s.dt.strftime('%Y/%m/%d')
0    2013/01/01
1    2013/01/02
2    2013/01/03
3    2013/01/04
dtype: object

The string format is as the python standard library and details can be found here


pd.Series of type timedelta64 has new method .dt.total_seconds() returning the duration of the timedelta in seconds (GH10817)

# TimedeltaIndex
In [19]: s = pd.Series(pd.timedelta_range('1 minutes', periods=4))

In [20]: s
0   0 days 00:01:00
1   1 days 00:01:00
2   2 days 00:01:00
3   3 days 00:01:00
dtype: timedelta64[ns]

In [21]: s.dt.total_seconds()
0        60
1     86460
2    172860
3    259260
dtype: float64

Period Frequency Enhancement

Period, PeriodIndex and period_range can now accept multiplied freq. Also, Period.freq and PeriodIndex.freq are now stored as a DateOffset instance like DatetimeIndex, and not as str (GH7811)

A multiplied freq represents a span of corresponding length. The example below creates a period of 3 days. Addition and subtraction will shift the period by its span.

In [22]: p = pd.Period('2015-08-01', freq='3D')

In [23]: p
Out[23]: Period('2015-08-01', '3D')

In [24]: p + 1
Out[24]: Period('2015-08-04', '3D')

In [25]: p - 2
Out[25]: Period('2015-07-26', '3D')

In [26]: p.to_timestamp()
Out[26]: Timestamp('2015-08-01 00:00:00')

In [27]: p.to_timestamp(how='E')
Out[27]: Timestamp('2015-08-03 00:00:00')

You can use the multiplied freq in PeriodIndex and period_range.

In [28]: idx = pd.period_range('2015-08-01', periods=4, freq='2D')

In [29]: idx
Out[29]: PeriodIndex(['2015-08-01', '2015-08-03', '2015-08-05', '2015-08-07'], dtype='int64', freq='2D')

In [30]: idx + 1
Out[30]: PeriodIndex(['2015-08-03', '2015-08-05', '2015-08-07', '2015-08-09'], dtype='int64', freq='2D')

Support for SAS XPORT files

read_sas() provides support for reading SAS XPORT format files. (GH4052).

df = pd.read_sas('sas_xport.xpt')

It is also possible to obtain an iterator and read an XPORT file incrementally.

for df in pd.read_sas('sas_xport.xpt', chunksize=10000)

See the docs for more details.

Support for Math Functions in .eval()

eval() now supports calling math functions (GH4893)

df = pd.DataFrame({'a': np.random.randn(10)})
df.eval("b = sin(a)")

The support math functions are sin, cos, exp, log, expm1, log1p, sqrt, sinh, cosh, tanh, arcsin, arccos, arctan, arccosh, arcsinh, arctanh, abs and arctan2.

These functions map to the intrinsics for the NumExpr engine. For the Python engine, they are mapped to NumPy calls.

Changes to Excel with MultiIndex

In version 0.16.2 a DataFrame with MultiIndex columns could not be written to Excel via to_excel. That functionality has been added (GH10564), along with updating read_excel so that the data can be read back with, no loss of information, by specifying which columns/rows make up the MultiIndex in the header and index_col parameters (GH4679)

See the documentation for more details.

In [31]: df = pd.DataFrame([[1,2,3,4], [5,6,7,8]],
   ....:                   columns = pd.MultiIndex.from_product([['foo','bar'],['a','b']],
   ....:                                                        names = ['col1', 'col2']),
   ....:                   index = pd.MultiIndex.from_product([['j'], ['l', 'k']],
   ....:                                                      names = ['i1', 'i2']))

In [32]: df
col1  foo    bar   
col2    a  b   a  b
i1 i2              
j  l    1  2   3  4
   k    5  6   7  8

In [33]: df.to_excel('test.xlsx')

In [34]: df = pd.read_excel('test.xlsx', header=[0,1], index_col=[0,1])

In [35]: df
col1  foo    bar   
col2    a  b   a  b
i1 i2              
j  l    1  2   3  4
   k    5  6   7  8

Previously, it was necessary to specify the has_index_names argument in read_excel, if the serialized data had index names. For version 0.17.0 the ouptput format of to_excel has been changed to make this keyword unnecessary - the change is shown below.






Excel files saved in version 0.16.2 or prior that had index names will still able to be read in, but the has_index_names argument must specified to True.

Google BigQuery Enhancements

  • Added ability to automatically create a table/dataset using the function if the destination table/dataset does not exist. (GH8325, GH11121).
  • Added ability to replace an existing table and schema when calling the function via the if_exists argument. See the docs for more details (GH8325).
  • InvalidColumnOrder and InvalidPageToken in the gbq module will raise ValueError instead of IOError.
  • The generate_bq_schema() function is now deprecated and will be removed in a future version (GH11121)
  • The gbq module will now support Python 3 (GH11094).

Display Alignment with Unicode East Asian Width


Enabling this option will affect the performance for printing of DataFrame and Series (about 2 times slower). Use only when it is actually required.

Some East Asian countries use Unicode characters its width is corresponding to 2 alphabets. If a DataFrame or Series contains these characters, the default output cannot be aligned properly. The following options are added to enable precise handling for these characters.

  • display.unicode.east_asian_width: Whether to use the Unicode East Asian Width to calculate the display text width. (GH2612)
  • display.unicode.ambiguous_as_wide: Whether to handle Unicode characters belong to Ambiguous as Wide. (GH11102)
In [36]: df = pd.DataFrame({u'国籍': ['UK', u'日本'], u'名前': ['Alice', u'しのぶ']})

In [37]: df;
In [38]: pd.set_option('display.unicode.east_asian_width', True)

In [39]: df;

For further details, see here

Other enhancements

  • Support for openpyxl >= 2.2. The API for style support is now stable (GH10125)

  • merge now accepts the argument indicator which adds a Categorical-type column (by default called _merge) to the output object that takes on the values (GH8790)

    Observation Origin _merge value
    Merge key only in 'left' frame left_only
    Merge key only in 'right' frame right_only
    Merge key in both frames both
    In [40]: df1 = pd.DataFrame({'col1':[0,1], 'col_left':['a','b']})
    In [41]: df2 = pd.DataFrame({'col1':[1,2,2],'col_right':[2,2,2]})
    In [42]: pd.merge(df1, df2, on='col1', how='outer', indicator=True)
       col1 col_left  col_right      _merge
    0     0        a        NaN   left_only
    1     1        b          2        both
    2     2      NaN          2  right_only
    3     2      NaN          2  right_only

    For more, see the updated docs

  • pd.to_numeric is a new function to coerce strings to numbers (possibly with coercion) (GH11133)

  • pd.merge will now allow duplicate column names if they are not merged upon (GH10639).

  • pd.pivot will now allow passing index as None (GH3962).

  • pd.concat will now use existing Series names if provided (GH10698).

    In [43]: foo = pd.Series([1,2], name='foo')
    In [44]: bar = pd.Series([1,2])
    In [45]: baz = pd.Series([4,5])

    Previous Behavior:

    In [1] pd.concat([foo, bar, baz], 1)
          0  1  2
       0  1  1  4
       1  2  2  5

    New Behavior:

    In [46]: pd.concat([foo, bar, baz], 1)
       foo  0  1
    0    1  1  4
    1    2  2  5
  • DataFrame has gained the nlargest and nsmallest methods (GH10393)

  • Add a limit_direction keyword argument that works with limit to enable interpolate to fill NaN values forward, backward, or both (GH9218, GH10420, GH11115)

    In [47]: ser = pd.Series([np.nan, np.nan, 5, np.nan, np.nan, np.nan, 13])
    In [48]: ser.interpolate(limit=1, limit_direction='both')
    0   NaN
    1     5
    2     5
    3     7
    4   NaN
    5    11
    6    13
    dtype: float64
  • Added a DataFrame.round method to round the values to a variable number of decimal places (GH10568).

    In [49]: df = pd.DataFrame(np.random.random([3, 3]), columns=['A', 'B', 'C'],
       ....: index=['first', 'second', 'third'])
    In [50]: df
                   A         B         C
    first   0.342764  0.304121  0.417022
    second  0.681301  0.875457  0.510422
    third   0.669314  0.585937  0.624904
    In [51]: df.round(2)
               A     B     C
    first   0.34  0.30  0.42
    second  0.68  0.88  0.51
    third   0.67  0.59  0.62
    In [52]: df.round({'A': 0, 'C': 2})
            A         B     C
    first   0  0.304121  0.42
    second  1  0.875457  0.51
    third   1  0.585937  0.62
  • drop_duplicates and duplicated now accept a keep keyword to target first, last, and all duplicates. The take_last keyword is deprecated, see here (GH6511, GH8505)

    In [53]: s = pd.Series(['A', 'B', 'C', 'A', 'B', 'D'])
    In [54]: s.drop_duplicates()
    0    A
    1    B
    2    C
    5    D
    dtype: object
    In [55]: s.drop_duplicates(keep='last')
    2    C
    3    A
    4    B
    5    D
    dtype: object
    In [56]: s.drop_duplicates(keep=False)
    2    C
    5    D
    dtype: object
  • Reindex now has a tolerance argument that allows for finer control of Limits on filling while reindexing (GH10411):

    In [57]: df = pd.DataFrame({'x': range(5),
       ....:                    't': pd.date_range('2000-01-01', periods=5)})
    In [58]: df.reindex([0.1, 1.9, 3.5],
       ....:            method='nearest',
       ....:            tolerance=0.2)
                 t   x
    0.1 2000-01-01   0
    1.9 2000-01-03   2
    3.5        NaT NaN

    When used on a DatetimeIndex, TimedeltaIndex or PeriodIndex, tolerance will coerced into a Timedelta if possible. This allows you to specify tolerance with a string:

    In [59]: df = df.set_index('t')
    In [60]: df.reindex(pd.to_datetime(['1999-12-31']),
       ....:            method='nearest',
       ....:            tolerance='1 day')
    1999-12-31  0

    tolerance is also exposed by the lower level Index.get_indexer and Index.get_loc methods.

  • Added functionality to use the base argument when resampling a TimeDeltaIndex (GH10530)

  • DatetimeIndex can be instantiated using strings contains NaT (GH7599)

  • to_datetime can now accept the yearfirst keyword (GH7599)

  • pandas.tseries.offsets larger than the Day offset can now be used with a Series for addition/subtraction (GH10699). See the docs for more details.

  • pd.Timedelta.total_seconds() now returns Timedelta duration to ns precision (previously microsecond precision) (GH10939)

  • PeriodIndex now supports arithmetic with np.ndarray (GH10638)

  • Support pickling of Period objects (GH10439)

  • .as_blocks will now take a copy optional argument to return a copy of the data, default is to copy (no change in behavior from prior versions), (GH9607)

  • regex argument to DataFrame.filter now handles numeric column names instead of raising ValueError (GH10384).

  • Enable reading gzip compressed files via URL, either by explicitly setting the compression parameter or by inferring from the presence of the HTTP Content-Encoding header in the response (GH8685)

  • Enable writing Excel files in memory using StringIO/BytesIO (GH7074)

  • Enable serialization of lists and dicts to strings in ExcelWriter (GH8188)

  • SQL io functions now accept a SQLAlchemy connectable. (GH7877)

  • pd.read_sql and to_sql can accept database URI as con parameter (GH10214)

  • read_sql_table will now allow reading from views (GH10750).

  • Enable writing complex values to HDFStores when using the table format (GH10447)

  • Enable pd.read_hdf to be used without specifying a key when the HDF file contains a single dataset (GH10443)

  • pd.read_stata will now read Stata 118 type files. (GH9882)

  • msgpack submodule has been updated to 0.4.6 with backward compatibility (GH10581)

  • DataFrame.to_dict now accepts orient='index' keyword argument (GH10844).

  • DataFrame.apply will return a Series of dicts if the passed function returns a dict and reduce=True (GH8735).

  • Allow passing kwargs to the interpolation methods (GH10378).

  • Improved error message when concatenating an empty iterable of Dataframe objects (GH9157)

  • pd.read_csv can now read bz2-compressed files incrementally, and the C parser can read bz2-compressed files from AWS S3 (GH11070, GH11072).

  • In pd.read_csv, recognize s3n:// and s3a:// URLs as designating S3 file storage (GH11070, GH11071).

  • Read CSV files from AWS S3 incrementally, instead of first downloading the entire file. (Full file download still required for compressed files in Python 2.) (GH11070, GH11073)

  • pd.read_csv is now able to infer compression type for files read from AWS S3 storage (GH11070, GH11074).

Backwards incompatible API changes

Changes to sorting API

The sorting API has had some longtime inconsistencies. (GH9816, GH8239).

Here is a summary of the API PRIOR to 0.17.0:

  • Series.sort is INPLACE while DataFrame.sort returns a new object.
  • Series.order returns a new object
  • It was possible to use Series/DataFrame.sort_index to sort by values by passing the by keyword.
  • Series/DataFrame.sortlevel worked only on a MultiIndex for sorting by index.

To address these issues, we have revamped the API:

  • We have introduced a new method, DataFrame.sort_values(), which is the merger of DataFrame.sort(), Series.sort(), and Series.order(), to handle sorting of values.
  • The existing methods Series.sort(), Series.order(), and DataFrame.sort() have been deprecated and will be removed in a future version.
  • The by argument of DataFrame.sort_index() has been deprecated and will be removed in a future version.
  • The existing method .sort_index() will gain the level keyword to enable level sorting.

We now have two distinct and non-overlapping methods of sorting. A * marks items that will show a FutureWarning.

To sort by the values:

Previous Replacement
* Series.order() Series.sort_values()
* Series.sort() Series.sort_values(inplace=True)
* DataFrame.sort(columns=...) DataFrame.sort_values(by=...)

To sort by the index:

Previous Replacement
Series.sort_index() Series.sort_index()
Series.sortlevel(level=...) Series.sort_index(level=...)
DataFrame.sort_index() DataFrame.sort_index()
DataFrame.sortlevel(level=...) DataFrame.sort_index(level=...)
* DataFrame.sort() DataFrame.sort_index()

We have also deprecated and changed similar methods in two Series-like classes, Index and Categorical.

Previous Replacement
* Index.order() Index.sort_values()
* Categorical.order() Categorical.sort_values()

Changes to to_datetime and to_timedelta

Error handling

The default for pd.to_datetime error handling has changed to errors='raise'. In prior versions it was errors='ignore'. Furthermore, the coerce argument has been deprecated in favor of errors='coerce'. This means that invalid parsing will raise rather that return the original input as in previous versions. (GH10636)

Previous Behavior:

In [2]: pd.to_datetime(['2009-07-31', 'asd'])
Out[2]: array(['2009-07-31', 'asd'], dtype=object)

New Behavior:

In [3]: pd.to_datetime(['2009-07-31', 'asd'])
ValueError: Unknown string format

Of course you can coerce this as well.

In [61]: to_datetime(['2009-07-31', 'asd'], errors='coerce')
Out[61]: DatetimeIndex(['2009-07-31', 'NaT'], dtype='datetime64[ns]', freq=None)

To keep the previous behavior, you can use errors='ignore':

In [62]: to_datetime(['2009-07-31', 'asd'], errors='ignore')
Out[62]: array(['2009-07-31', 'asd'], dtype=object)

Furthermore, pd.to_timedelta has gained a similar API, of errors='raise'|'ignore'|'coerce', and the coerce keyword has been deprecated in favor of errors='coerce'.

Consistent Parsing

The string parsing of to_datetime, Timestamp and DatetimeIndex has been made consistent. (GH7599)

Prior to v0.17.0, Timestamp and to_datetime may parse year-only datetime-string incorrectly using today’s date, otherwise DatetimeIndex uses the beginning of the year. Timestamp and to_datetime may raise ValueError in some types of datetime-string which DatetimeIndex can parse, such as a quarterly string.

Previous Behavior:

In [1]: Timestamp('2012Q2')
ValueError: Unable to parse 2012Q2

# Results in today's date.
In [2]: Timestamp('2014')
Out [2]: 2014-08-12 00:00:00

v0.17.0 can parse them as below. It works on DatetimeIndex also.

New Behavior:

In [63]: Timestamp('2012Q2')
Out[63]: Timestamp('2012-04-01 00:00:00')

In [64]: Timestamp('2014')
Out[64]: Timestamp('2014-01-01 00:00:00')

In [65]: DatetimeIndex(['2012Q2', '2014'])
Out[65]: DatetimeIndex(['2012-04-01', '2014-01-01'], dtype='datetime64[ns]', freq=None)


If you want to perform calculations based on today’s date, use and pandas.tseries.offsets.

In [66]: import pandas.tseries.offsets as offsets

In [67]:
Out[67]: Timestamp('2015-11-21 02:38:37.772350')

In [68]: + offsets.DateOffset(years=1)
Out[68]: Timestamp('2016-11-21 02:38:37.906963')

Changes to Index Comparisons

Operator equal on Index should behavior similarly to Series (GH9947, GH10637)

Starting in v0.17.0, comparing Index objects of different lengths will raise a ValueError. This is to be consistent with the behavior of Series.

Previous Behavior:

In [2]: pd.Index([1, 2, 3]) == pd.Index([1, 4, 5])
Out[2]: array([ True, False, False], dtype=bool)

In [3]: pd.Index([1, 2, 3]) == pd.Index([2])
Out[3]: array([False,  True, False], dtype=bool)

In [4]: pd.Index([1, 2, 3]) == pd.Index([1, 2])
Out[4]: False

New Behavior:

In [8]: pd.Index([1, 2, 3]) == pd.Index([1, 4, 5])
Out[8]: array([ True, False, False], dtype=bool)

In [9]: pd.Index([1, 2, 3]) == pd.Index([2])
ValueError: Lengths must match to compare

In [10]: pd.Index([1, 2, 3]) == pd.Index([1, 2])
ValueError: Lengths must match to compare

Note that this is different from the numpy behavior where a comparison can be broadcast:

In [69]: np.array([1, 2, 3]) == np.array([1])
Out[69]: array([ True, False, False], dtype=bool)

or it can return False if broadcasting can not be done:

In [70]: np.array([1, 2, 3]) == np.array([1, 2])
Out[70]: False

Changes to Boolean Comparisons vs. None

Boolean comparisons of a Series vs None will now be equivalent to comparing with np.nan, rather than raise TypeError. (GH1079).

In [71]: s = Series(range(3))

In [72]: s.iloc[1] = None

In [73]: s
0     0
1   NaN
2     2
dtype: float64

Previous Behavior:

In [5]: s==None
TypeError: Could not compare <type 'NoneType'> type with Series

New Behavior:

In [74]: s==None
0    False
1    False
2    False
dtype: bool

Usually you simply want to know which values are null.

In [75]: s.isnull()
0    False
1     True
2    False
dtype: bool


You generally will want to use isnull/notnull for these types of comparisons, as isnull/notnull tells you which elements are null. One has to be mindful that nan's don’t compare equal, but None's do. Note that Pandas/numpy uses the fact that np.nan != np.nan, and treats None like np.nan.

In [76]: None == None
Out[76]: True

In [77]: np.nan == np.nan
Out[77]: False

HDFStore dropna behavior

The default behavior for HDFStore write functions with format='table' is now to keep rows that are all missing. Previously, the behavior was to drop rows that were all missing save the index. The previous behavior can be replicated using the dropna=True option. (GH9382)

Previous Behavior:

In [78]: df_with_missing = pd.DataFrame({'col1':[0, np.nan, 2],
   ....:                                 'col2':[1, np.nan, np.nan]})

In [79]: df_with_missing
   col1  col2
0     0     1
1   NaN   NaN
2     2   NaN
In [28]:

pd.read_hdf('file.h5', 'df_with_missing')

Out [28]:
      col1  col2
  0     0     1
  2     2   NaN

New Behavior:

In [80]: df_with_missing.to_hdf('file.h5',
   ....:                        'df_with_missing',
   ....:                         format='table',
   ....:                         mode='w')

In [81]: pd.read_hdf('file.h5', 'df_with_missing')
   col1  col2
0     0     1
1   NaN   NaN
2     2   NaN

See the docs for more details.

Changes to display.precision option

The display.precision option has been clarified to refer to decimal places (GH10451).

Earlier versions of pandas would format floating point numbers to have one less decimal place than the value in display.precision.

In [1]: pd.set_option('display.precision', 2)

In [2]: pd.DataFrame({'x': [123.456789]})
0  123.5

If interpreting precision as “significant figures” this did work for scientific notation but that same interpretation did not work for values with standard formatting. It was also out of step with how numpy handles formatting.

Going forward the value of display.precision will directly control the number of places after the decimal, for regular formatting as well as scientific notation, similar to how numpy’s precision print option works.

In [82]: pd.set_option('display.precision', 2)

In [83]: pd.DataFrame({'x': [123.456789]})
0  123.46

To preserve output behavior with prior versions the default value of display.precision has been reduced to 6 from 7.

Changes to Categorical.unique

Categorical.unique now returns new Categoricals with categories and codes that are unique, rather than returning np.array (GH10508)

  • unordered category: values and categories are sorted by appearance order.
  • ordered category: values are sorted by appearance order, categories keep existing order.
In [84]: cat = pd.Categorical(['C', 'A', 'B', 'C'],
   ....:                      categories=['A', 'B', 'C'],
   ....:                      ordered=True)

In [85]: cat
[C, A, B, C]
Categories (3, object): [A < B < C]

In [86]: cat.unique()
[C, A, B]
Categories (3, object): [A < B < C]

In [87]: cat = pd.Categorical(['C', 'A', 'B', 'C'],
   ....:                      categories=['A', 'B', 'C'])

In [88]: cat
[C, A, B, C]
Categories (3, object): [A, B, C]

In [89]: cat.unique()
[C, A, B]
Categories (3, object): [C, A, B]

Changes to bool passed as header in Parsers

In earlier versions of pandas, if a bool was passed the header argument of read_csv, read_excel, or read_html it was implicitly converted to an integer, resulting in header=0 for False and header=1 for True (GH6113)

A bool input to header will now raise a TypeError

In [29]: df = pd.read_csv('data.csv', header=False)
TypeError: Passing a bool to header is invalid. Use header=None for no header or
header=int or list-like of ints to specify the row(s) making up the column names

Other API Changes

  • Line and kde plot with subplots=True now uses default colors, not all black. Specify color='k' to draw all lines in black (GH9894)

  • Calling the .value_counts() method on a Series with a categorical dtype now returns a Series with a CategoricalIndex (GH10704)

  • The metadata properties of subclasses of pandas objects will now be serialized (GH10553).

  • groupby using Categorical follows the same rule as Categorical.unique described above (GH10508)

  • When constructing DataFrame with an array of complex64 dtype previously meant the corresponding column was automatically promoted to the complex128 dtype. Pandas will now preserve the itemsize of the input for complex data (GH10952)

  • some numeric reduction operators would return ValueError, rather than TypeError on object types that includes strings and numbers (GH11131)

  • Passing currently unsupported chunksize argument to read_excel or ExcelFile.parse will now raise NotImplementedError (GH8011)

  • Allow an ExcelFile object to be passed into read_excel (GH11198)

  • DatetimeIndex.union does not infer freq if self and the input have None as freq (GH11086)

  • NaT‘s methods now either raise ValueError, or return np.nan or NaT (GH9513)

    Behavior Methods
    return np.nan weekday, isoweekday
    return NaT date, now, replace, to_datetime, today
    return np.datetime64('NaT') to_datetime64 (unchanged)
    raise ValueError All other public methods (names not beginning with underscores)


  • For Series the following indexing functions are deprecated (GH10177).

    Deprecated Function Replacement
    .irow(i) .iloc[i] or .iat[i]
    .iget(i) .iloc[i] or .iat[i]
    .iget_value(i) .iloc[i] or .iat[i]
  • For DataFrame the following indexing functions are deprecated (GH10177).

    Deprecated Function Replacement
    .irow(i) .iloc[i]
    .iget_value(i, j) .iloc[i, j] or .iat[i, j]
    .icol(j) .iloc[:, j]


These indexing function have been deprecated in the documentation since 0.11.0.

  • was deprecated to make Categorical more numpy.ndarray like. Use Series(cat, name="whatever") instead (GH10482).
  • Setting missing values (NaN) in a Categorical‘s categories will issue a warning (GH10748). You can still have missing values in the values.
  • drop_duplicates and duplicated‘s take_last keyword was deprecated in favor of keep. (GH6511, GH8505)
  • Series.nsmallest and nlargest‘s take_last keyword was deprecated in favor of keep. (GH10792)
  • DataFrame.combineAdd and DataFrame.combineMult are deprecated. They can easily be replaced by using the add and mul methods: DataFrame.add(other, fill_value=0) and DataFrame.mul(other, fill_value=1.) (GH10735).
  • TimeSeries deprecated in favor of Series (note that this has been an alias since 0.13.0), (GH10890)
  • SparsePanel deprecated and will be removed in a future version (GH11157).
  • Series.is_time_series deprecated in favor of Series.index.is_all_dates (GH11135)
  • Legacy offsets (like 'A@JAN') listed in here are deprecated (note that this has been alias since 0.8.0), (GH10878)
  • WidePanel deprecated in favor of Panel, LongPanel in favor of DataFrame (note these have been aliases since < 0.11.0), (GH10892)
  • DataFrame.convert_objects has been deprecated in favor of type-specific functions pd.to_datetime, pd.to_timestamp and pd.to_numeric (new in 0.17.0) (GH11133).

Removal of prior version deprecations/changes

  • Removal of na_last parameters from Series.order() and Series.sort(), in favor of na_position. (GH5231)

  • Remove of percentile_width from .describe(), in favor of percentiles. (GH7088)

  • Removal of colSpace parameter from DataFrame.to_string(), in favor of col_space, circa 0.8.0 version.

  • Removal of automatic time-series broadcasting (GH2304)

    In [90]: np.random.seed(1234)
    In [91]: df = DataFrame(np.random.randn(5,2),columns=list('AB'),index=date_range('20130101',periods=5))
    In [92]: df
                       A         B
    2013-01-01  0.471435 -1.190976
    2013-01-02  1.432707 -0.312652
    2013-01-03 -0.720589  0.887163
    2013-01-04  0.859588 -0.636524
    2013-01-05  0.015696 -2.242685


    In [3]: df + df.A
    FutureWarning: TimeSeries broadcasting along DataFrame index by default is deprecated.
    Please use DataFrame.<op> to explicitly broadcast arithmetic operations along the index
                        A         B
    2013-01-01  0.942870 -0.719541
    2013-01-02  2.865414  1.120055
    2013-01-03 -1.441177  0.166574
    2013-01-04  1.719177  0.223065
    2013-01-05  0.031393 -2.226989


    In [93]: df.add(df.A,axis='index')
                       A         B
    2013-01-01  0.942870 -0.719541
    2013-01-02  2.865414  1.120055
    2013-01-03 -1.441177  0.166574
    2013-01-04  1.719177  0.223065
    2013-01-05  0.031393 -2.226989
  • Remove table keyword in HDFStore.put/append, in favor of using format= (GH4645)

  • Remove kind in read_excel/ExcelFile as its unused (GH4712)

  • Remove infer_type keyword from pd.read_html as its unused (GH4770, GH7032)

  • Remove offset and timeRule keywords from Series.tshift/shift, in favor of freq (GH4853, GH4864)

  • Remove pd.load/ aliases in favor of pd.to_pickle/pd.read_pickle (GH3787)

Performance Improvements

  • Development support for benchmarking with the Air Speed Velocity library (GH8361)
  • Added vbench benchmarks for alternative ExcelWriter engines and reading Excel files (GH7171)
  • Performance improvements in Categorical.value_counts (GH10804)
  • Performance improvements in SeriesGroupBy.nunique and SeriesGroupBy.value_counts and SeriesGroupby.transform (GH10820, GH11077)
  • Performance improvements in DataFrame.drop_duplicates with integer dtypes (GH10917)
  • Performance improvements in DataFrame.duplicated with wide frames. (GH10161, GH11180)
  • 4x improvement in timedelta string parsing (GH6755, GH10426)
  • 8x improvement in timedelta64 and datetime64 ops (GH6755)
  • Significantly improved performance of indexing MultiIndex with slicers (GH10287)
  • 8x improvement in iloc using list-like input (GH10791)
  • Improved performance of Series.isin for datetimelike/integer Series (GH10287)
  • 20x improvement in concat of Categoricals when categories are identical (GH10587)
  • Improved performance of to_datetime when specified format string is ISO8601 (GH10178)
  • 2x improvement of Series.value_counts for float dtype (GH10821)
  • Enable infer_datetime_format in to_datetime when date components do not have 0 padding (GH11142)
  • Regression from 0.16.1 in constructing DataFrame from nested dictionary (GH11084)
  • Performance improvements in addition/subtraction operations for DateOffset with Series or DatetimeIndex (GH10744, GH11205)

Bug Fixes

  • Bug in incorrection computation of .mean() on timedelta64[ns] because of overflow (GH9442)
  • Bug in .isin on older numpies (:issue: 11232)
  • Bug in DataFrame.to_html(index=False) renders unnecessary name row (GH10344)
  • Bug in DataFrame.to_latex() the column_format argument could not be passed (GH9402)
  • Bug in DatetimeIndex when localizing with NaT (GH10477)
  • Bug in Series.dt ops in preserving meta-data (GH10477)
  • Bug in preserving NaT when passed in an otherwise invalid to_datetime construction (GH10477)
  • Bug in DataFrame.apply when function returns categorical series. (GH9573)
  • Bug in to_datetime with invalid dates and formats supplied (GH10154)
  • Bug in Index.drop_duplicates dropping name(s) (GH10115)
  • Bug in Series.quantile dropping name (GH10881)
  • Bug in pd.Series when setting a value on an empty Series whose index has a frequency. (GH10193)
  • Bug in pd.Series.interpolate with invalid order keyword values. (GH10633)
  • Bug in DataFrame.plot raises ValueError when color name is specified by multiple characters (GH10387)
  • Bug in Index construction with a mixed list of tuples (GH10697)
  • Bug in DataFrame.reset_index when index contains NaT. (GH10388)
  • Bug in ExcelReader when worksheet is empty (GH6403)
  • Bug in BinGrouper.group_info where returned values are not compatible with base class (GH10914)
  • Bug in clearing the cache on DataFrame.pop and a subsequent inplace op (GH10912)
  • Bug in indexing with a mixed-integer Index causing an ImportError (GH10610)
  • Bug in Series.count when index has nulls (GH10946)
  • Bug in pickling of a non-regular freq DatetimeIndex (GH11002)
  • Bug causing DataFrame.where to not respect the axis parameter when the frame has a symmetric shape. (GH9736)
  • Bug in Table.select_column where name is not preserved (GH10392)
  • Bug in offsets.generate_range where start and end have finer precision than offset (GH9907)
  • Bug in pd.rolling_* where would be lost in the output (GH10565)
  • Bug in stack when index or columns are not unique. (GH10417)
  • Bug in setting a Panel when an axis has a multi-index (GH10360)
  • Bug in USFederalHolidayCalendar where USMemorialDay and USMartinLutherKingJr were incorrect (GH10278 and GH9760 )
  • Bug in .sample() where returned object, if set, gives unnecessary SettingWithCopyWarning (GH10738)
  • Bug in .sample() where weights passed as Series were not aligned along axis before being treated positionally, potentially causing problems if weight indices were not aligned with sampled object. (GH10738)
  • Regression fixed in (GH9311, GH6620, GH9345), where groupby with a datetime-like converting to float with certain aggregators (GH10979)
  • Bug in DataFrame.interpolate with axis=1 and inplace=True (GH10395)
  • Bug in io.sql.get_schema when specifying multiple columns as primary key (GH10385).
  • Bug in groupby(sort=False) with datetime-like Categorical raises ValueError (GH10505)
  • Bug in groupby(axis=1) with filter() throws IndexError (GH11041)
  • Bug in test_categorical on big-endian builds (GH10425)
  • Bug in Series.shift and DataFrame.shift not supporting categorical data (GH9416)
  • Bug in using categorical Series raises AttributeError (GH10324)
  • Bug in MultiIndex.get_level_values including Categorical raises AttributeError (GH10460)
  • Bug in pd.get_dummies with sparse=True not returning SparseDataFrame (GH10531)
  • Bug in Index subtypes (such as PeriodIndex) not returning their own type for .drop and .insert methods (GH10620)
  • Bug in algos.outer_join_indexer when right array is empty (GH10618)
  • Bug in filter (regression from 0.16.0) and transform when grouping on multiple keys, one of which is datetime-like (GH10114)
  • Bug in to_datetime and to_timedelta causing Index name to be lost (GH10875)
  • Bug in len(DataFrame.groupby) causing IndexError when there’s a column containing only NaNs (:issue: 11016)
  • Bug that caused segfault when resampling an empty Series (GH10228)
  • Bug in DatetimeIndex and PeriodIndex.value_counts resets name from its result, but retains in result’s Index. (GH10150)
  • Bug in pd.eval using numexpr engine coerces 1 element numpy array to scalar (GH10546)
  • Bug in pd.concat with axis=0 when column is of dtype category (GH10177)
  • Bug in read_msgpack where input type is not always checked (GH10369, GH10630)
  • Bug in pd.read_csv with kwargs index_col=False, index_col=['a', 'b'] or dtype (GH10413, GH10467, GH10577)
  • Bug in Series.from_csv with header kwarg not setting the or the (GH10483)
  • Bug in groupby.var which caused variance to be inaccurate for small float values (GH10448)
  • Bug in Series.plot(kind='hist') Y Label not informative (GH10485)
  • Bug in read_csv when using a converter which generates a uint8 type (GH9266)
  • Bug causes memory leak in time-series line and area plot (GH9003)
  • Bug when setting a Panel sliced along the major or minor axes when the right-hand side is a DataFrame (GH11014)
  • Bug that returns None and does not raise NotImplementedError when operator functions (e.g. .add) of Panel are not implemented (GH7692)
  • Bug in line and kde plot cannot accept multiple colors when subplots=True (GH9894)
  • Bug in DataFrame.plot raises ValueError when color name is specified by multiple characters (GH10387)
  • Bug in left and right align of Series with MultiIndex may be inverted (GH10665)
  • Bug in left and right join of with MultiIndex may be inverted (GH10741)
  • Bug in read_stata when reading a file with a different order set in columns (GH10757)
  • Bug in Categorical may not representing properly when category contains tz or Period (GH10713)
  • Bug in Categorical.__iter__ may not returning correct datetime and Period (GH10713)
  • Bug in indexing with a PeriodIndex on an object with a PeriodIndex (GH4125)
  • Bug in read_csv with engine='c': EOF preceded by a comment, blank line, etc. was not handled correctly (GH10728, GH10548)
  • Reading “famafrench” data via DataReader results in HTTP 404 error because of the website url is changed (GH10591).
  • Bug in read_msgpack where DataFrame to decode has duplicate column names (GH9618)
  • Bug in io.common.get_filepath_or_buffer which caused reading of valid S3 files to fail if the bucket also contained keys for which the user does not have read permission (GH10604)
  • Bug in vectorised setting of timestamp columns with python and numpy datetime64 (GH10408, GH10412)
  • Bug in Index.take may add unnecessary freq attribute (GH10791)
  • Bug in merge with empty DataFrame may raise IndexError (GH10824)
  • Bug in to_latex where unexpected keyword argument for some documented arguments (GH10888)
  • Bug in indexing of large DataFrame where IndexError is uncaught (GH10645 and GH10692)
  • Bug in read_csv when using the nrows or chunksize parameters if file contains only a header line (GH9535)
  • Bug in serialization of category types in HDF5 in presence of alternate encodings. (GH10366)
  • Bug in pd.DataFrame when constructing an empty DataFrame with a string dtype (GH9428)
  • Bug in pd.DataFrame.diff when DataFrame is not consolidated (GH10907)
  • Bug in pd.unique for arrays with the datetime64 or timedelta64 dtype that meant an array with object dtype was returned instead the original dtype (GH9431)
  • Bug in Timedelta raising error when slicing from 0s (GH10583)
  • Bug in DatetimeIndex.take and TimedeltaIndex.take may not raise IndexError against invalid index (GH10295)
  • Bug in Series([np.nan]).astype('M8[ms]'), which now returns Series([pd.NaT]) (GH10747)
  • Bug in PeriodIndex.order reset freq (GH10295)
  • Bug in date_range when freq divides end as nanos (GH10885)
  • Bug in iloc allowing memory outside bounds of a Series to be accessed with negative integers (GH10779)
  • Bug in read_msgpack where encoding is not respected (GH10581)
  • Bug preventing access to the first index when using iloc with a list containing the appropriate negative integer (GH10547, GH10779)
  • Bug in TimedeltaIndex formatter causing error while trying to save DataFrame with TimedeltaIndex using to_csv (GH10833)
  • Bug in DataFrame.where when handling Series slicing (GH10218, GH9558)
  • Bug where pd.read_gbq throws ValueError when Bigquery returns zero rows (GH10273)
  • Bug in to_json which was causing segmentation fault when serializing 0-rank ndarray (GH9576)
  • Bug in plotting functions may raise IndexError when plotted on GridSpec (GH10819)
  • Bug in plot result may show unnecessary minor ticklabels (GH10657)
  • Bug in groupby incorrect computation for aggregation on DataFrame with NaT (E.g first, last, min). (GH10590, GH11010)
  • Bug when constructing DataFrame where passing a dictionary with only scalar values and specifying columns did not raise an error (GH10856)
  • Bug in .var() causing roundoff errors for highly similar values (GH10242)
  • Bug in DataFrame.plot(subplots=True) with duplicated columns outputs incorrect result (GH10962)
  • Bug in Index arithmetic may result in incorrect class (GH10638)
  • Bug in date_range results in empty if freq is negative annualy, quarterly and monthly (GH11018)
  • Bug in DatetimeIndex cannot infer negative freq (GH11018)
  • Remove use of some deprecated numpy comparison operations, mainly in tests. (GH10569)
  • Bug in Index dtype may not applied properly (GH11017)
  • Bug in io.gbq when testing for minimum google api client version (GH10652)
  • Bug in DataFrame construction from nested dict with timedelta keys (GH11129)
  • Bug in .fillna against may raise TypeError when data contains datetime dtype (GH7095, GH11153)
  • Bug in .groupby when number of keys to group by is same as length of index (GH11185)
  • Bug in convert_objects where converted values might not be returned if all null and coerce (GH9589)
  • Bug in convert_objects where copy keyword was not respected (GH9589)

v0.16.2 (June 12, 2015)

This is a minor bug-fix release from 0.16.1 and includes a a large number of bug fixes along some new features (pipe() method), enhancements, and performance improvements.

We recommend that all users upgrade to this version.

Highlights include:

  • A new pipe method, see here
  • Documentation on how to use numba with pandas, see here

New features


We’ve introduced a new method DataFrame.pipe(). As suggested by the name, pipe should be used to pipe data through a chain of function calls. The goal is to avoid confusing nested function calls like

# df is a DataFrame
# f, g, and h are functions that take and return DataFrames
f(g(h(df), arg1=1), arg2=2, arg3=3)

The logic flows from inside out, and function names are separated from their keyword arguments. This can be rewritten as

   .pipe(g, arg1=1)
   .pipe(f, arg2=2, arg3=3)

Now both the code and the logic flow from top to bottom. Keyword arguments are next to their functions. Overall the code is much more readable.

In the example above, the functions f, g, and h each expected the DataFrame as the first positional argument. When the function you wish to apply takes its data anywhere other than the first argument, pass a tuple of (function, keyword) indicating where the DataFrame should flow. For example:

In [1]: import statsmodels.formula.api as sm

In [2]: bb = pd.read_csv('data/baseball.csv', index_col='id')

# sm.poisson takes (formula, data)
In [3]: (bb.query('h > 0')
   ...:    .assign(ln_h = lambda df: np.log(df.h))
   ...:    .pipe((sm.poisson, 'data'), 'hr ~ ln_h + year + g + C(lg)')
   ...:    .fit()
   ...:    .summary()
   ...: )
Optimization terminated successfully.
         Current function value: 2.116284
         Iterations 24
<class 'statsmodels.iolib.summary.Summary'>
                          Poisson Regression Results                          
Dep. Variable:                     hr   No. Observations:                   68
Model:                        Poisson   Df Residuals:                       63
Method:                           MLE   Df Model:                            4
Date:                Sat, 21 Nov 2015   Pseudo R-squ.:                  0.6878
Time:                        02:38:40   Log-Likelihood:                -143.91
converged:                       True   LL-Null:                       -460.91
                                        LLR p-value:                6.774e-136
                  coef    std err          z      P>|z|      [95.0% Conf. Int.]
Intercept   -1267.3636    457.867     -2.768      0.006     -2164.767  -369.960
C(lg)[T.NL]    -0.2057      0.101     -2.044      0.041        -0.403    -0.008
ln_h            0.9280      0.191      4.866      0.000         0.554     1.302
year            0.6301      0.228      2.762      0.006         0.183     1.077
g               0.0099      0.004      2.754      0.006         0.003     0.017

The pipe method is inspired by unix pipes, which stream text through processes. More recently dplyr and magrittr have introduced the popular (%>%) pipe operator for R.

See the documentation for more. (GH10129)

Other Enhancements

  • Added rsplit to Index/Series StringMethods (GH10303)

  • Removed the hard-coded size limits on the DataFrame HTML representation in the IPython notebook, and leave this to IPython itself (only for IPython v3.0 or greater). This eliminates the duplicate scroll bars that appeared in the notebook with large frames (GH10231).

    Note that the notebook has a toggle output scrolling feature to limit the display of very large frames (by clicking left of the output). You can also configure the way DataFrames are displayed using the pandas options, see here here.

  • axis parameter of DataFrame.quantile now accepts also index and column. (GH9543)

API Changes

  • Holiday now raises NotImplementedError if both offset and observance are used in the constructor instead of returning an incorrect result (GH10217).

Performance Improvements

  • Improved Series.resample performance with dtype=datetime64[ns] (GH7754)
  • Increase performance of str.split when expand=True (GH10081)

Bug Fixes

  • Bug in Series.hist raises an error when a one row Series was given (GH10214)
  • Bug where modifies the passed columns list (GH7212)
  • Bug in Categorical repr with display.width of None in Python 3 (GH10087)
  • Bug in to_json with certain orients and a CategoricalIndex would segfault (GH10317)
  • Bug where some of the nan funcs do not have consistent return dtypes (GH10251)
  • Bug in DataFrame.quantile on checking that a valid axis was passed (GH9543)
  • Bug in groupby.apply aggregation for Categorical not preserving categories (GH10138)
  • Bug in to_csv where date_format is ignored if the datetime is fractional (GH10209)
  • Bug in DataFrame.to_json with mixed data types (GH10289)
  • Bug in cache updating when consolidating (GH10264)
  • Bug in mean() where integer dtypes can overflow (GH10172)
  • Bug where Panel.from_dict does not set dtype when specified (GH10058)
  • Bug in Index.union raises AttributeError when passing array-likes. (GH10149)
  • Bug in Timestamp‘s’ microsecond, quarter, dayofyear, week and daysinmonth properties return type, not built-in int. (GH10050)
  • Bug in NaT raises AttributeError when accessing to daysinmonth, dayofweek properties. (GH10096)
  • Bug in Index repr when using the max_seq_items=None setting (GH10182).
  • Bug in getting timezone data with dateutil on various platforms ( GH9059, GH8639, GH9663, GH10121)
  • Bug in displaying datetimes with mixed frequencies; display ‘ms’ datetimes to the proper precision. (GH10170)
  • Bug in setitem where type promotion is applied to the entire block (GH10280)
  • Bug in Series arithmetic methods may incorrectly hold names (GH10068)
  • Bug in GroupBy.get_group when grouping on multiple keys, one of which is categorical. (GH10132)
  • Bug in DatetimeIndex and TimedeltaIndex names are lost after timedelta arithmetics ( GH9926)
  • Bug in DataFrame construction from nested dict with datetime64 (GH10160)
  • Bug in Series construction from dict with datetime64 keys (GH9456)
  • Bug in Series.plot(label="LABEL") not correctly setting the label (GH10119)
  • Bug in plot not defaulting to matplotlib axes.grid setting (GH9792)
  • Bug causing strings containing an exponent, but no decimal to be parsed as int instead of float in engine='python' for the read_csv parser (GH9565)
  • Bug in Series.align resets name when fill_value is specified (GH10067)
  • Bug in read_csv causing index name not to be set on an empty DataFrame (GH10184)
  • Bug in SparseSeries.abs resets name (GH10241)
  • Bug in TimedeltaIndex slicing may reset freq (GH10292)
  • Bug in GroupBy.get_group raises ValueError when group key contains NaT (GH6992)
  • Bug in SparseSeries constructor ignores input data name (GH10258)
  • Bug in Categorical.remove_categories causing a ValueError when removing the NaN category if underlying dtype is floating-point (GH10156)
  • Bug where infer_freq infers timerule (WOM-5XXX) unsupported by to_offset (GH9425)
  • Bug in DataFrame.to_hdf() where table format would raise a seemingly unrelated error for invalid (non-string) column names. This is now explicitly forbidden. (GH9057)
  • Bug to handle masking empty DataFrame (GH10126).
  • Bug where MySQL interface could not handle numeric table/column names (GH10255)
  • Bug in read_csv with a date_parser that returned a datetime64 array of other time resolution than [ns] (GH10245)
  • Bug in Panel.apply when the result has ndim=0 (GH10332)
  • Bug in read_hdf where auto_close could not be passed (GH9327).
  • Bug in read_hdf where open stores could not be used (GH10330).
  • Bug in adding empty DataFrame``s, now results in a ``DataFrame that .equals an empty DataFrame (GH10181).
  • Bug in to_hdf and HDFStore which did not check that complib choices were valid (GH4582, GH8874).

v0.16.1 (May 11, 2015)

This is a minor bug-fix release from 0.16.0 and includes a a large number of bug fixes along several new features, enhancements, and performance improvements. We recommend that all users upgrade to this version.

Highlights include:

  • Support for a CategoricalIndex, a category based index, see here
  • New section on how-to-contribute to pandas, see here
  • Revised “Merge, join, and concatenate” documentation, including graphical examples to make it easier to understand each operations, see here
  • New method sample for drawing random samples from Series, DataFrames and Panels. See here
  • The default Index printing has changed to a more uniform format, see here
  • BusinessHour datetime-offset is now supported, see here
  • Further enhancement to the .str accessor to make string operations easier, see here


In pandas 0.17.0, the sub-package will be removed in favor of a separately installable package. See here for details (GH8961)



We introduce a CategoricalIndex, a new type of index object that is useful for supporting indexing with duplicates. This is a container around a Categorical (introduced in v0.15.0) and allows efficient indexing and storage of an index with a large number of duplicated elements. Prior to 0.16.1, setting the index of a DataFrame/Series with a category dtype would convert this to regular object-based Index.

In [1]: df = DataFrame({'A' : np.arange(6),
   ...:                 'B' : Series(list('aabbca')).astype('category',
   ...:                                                     categories=list('cab'))
   ...:                })

In [2]: df
   A  B
0  0  a
1  1  a
2  2  b
3  3  b
4  4  c
5  5  a

In [3]: df.dtypes
A       int32
B    category
dtype: object

In [4]:
Out[4]: Index([u'c', u'a', u'b'], dtype='object')

setting the index, will create create a CategoricalIndex

In [5]: df2 = df.set_index('B')

In [6]: df2.index
Out[6]: CategoricalIndex([u'a', u'a', u'b', u'b', u'c', u'a'], categories=[u'c', u'a', u'b'], ordered=False, name=u'B', dtype='category')

indexing with __getitem__/.iloc/.loc/.ix works similarly to an Index with duplicates. The indexers MUST be in the category or the operation will raise.

In [7]: df2.loc['a']
a  0
a  1
a  5

and preserves the CategoricalIndex

In [8]: df2.loc['a'].index
Out[8]: CategoricalIndex([u'a', u'a', u'a'], categories=[u'c', u'a', u'b'], ordered=False, name=u'B', dtype='category')

sorting will order by the order of the categories

In [9]: df2.sort_index()
c  4
a  0
a  1
a  5
b  2
b  3

groupby operations on the index will preserve the index nature as well

In [10]: df2.groupby(level=0).sum()
c  4
a  6
b  5

In [11]: df2.groupby(level=0).sum().index
Out[11]: CategoricalIndex([u'c', u'a', u'b'], categories=[u'c', u'a', u'b'], ordered=False, name=u'B', dtype='category')

reindexing operations, will return a resulting index based on the type of the passed indexer, meaning that passing a list will return a plain-old-Index; indexing with a Categorical will return a CategoricalIndex, indexed according to the categories of the PASSED Categorical dtype. This allows one to arbitrarly index these even with values NOT in the categories, similarly to how you can reindex ANY pandas index.

In [12]: df2.reindex(['a','e'])
a   0
a   1
a   5
e NaN

In [13]: df2.reindex(['a','e']).index
Out[13]: Index([u'a', u'a', u'a', u'e'], dtype='object', name=u'B')

In [14]: df2.reindex(pd.Categorical(['a','e'],categories=list('abcde')))
a   0
a   1
a   5
e NaN

In [15]: df2.reindex(pd.Categorical(['a','e'],categories=list('abcde'))).index
Out[15]: CategoricalIndex([u'a', u'a', u'a', u'e'], categories=[u'a', u'e'], ordered=False, name=u'B', dtype='category')

See the documentation for more. (GH7629, GH10038, GH10039)


Series, DataFrames, and Panels now have a new method: sample(). The method accepts a specific number of rows or columns to return, or a fraction of the total number or rows or columns. It also has options for sampling with or without replacement, for passing in a column for weights for non-uniform sampling, and for setting seed values to facilitate replication. (GH2419)

In [16]: example_series = Series([0,1,2,3,4,5])

# When no arguments are passed, returns 1
In [17]: example_series.sample()
4    4
dtype: int64

# One may specify either a number of rows:
In [18]: example_series.sample(n=3)
2    2
0    0
4    4
dtype: int64

# Or a fraction of the rows:
In [19]: example_series.sample(frac=0.5)
3    3
4    4
0    0
dtype: int64

# weights are accepted.
In [20]: example_weights = [0, 0, 0.2, 0.2, 0.2, 0.4]

In [21]: example_series.sample(n=3, weights=example_weights)
5    5
4    4
2    2
dtype: int64

# weights will also be normalized if they do not sum to one,
# and missing values will be treated as zeros.
In [22]: example_weights2 = [0.5, 0, 0, 0, None, np.nan]

In [23]: example_series.sample(n=1, weights=example_weights2)
0    0
dtype: int64

When applied to a DataFrame, one may pass the name of a column to specify sampling weights when sampling from rows.

In [24]: df = DataFrame({'col1':[9,8,7,6], 'weight_column':[0.5, 0.4, 0.1, 0]})

In [25]: df.sample(n=3, weights='weight_column')
   col1  weight_column
0     9            0.5
2     7            0.1
1     8            0.4

String Methods Enhancements

Continuing from v0.16.0, the following enhancements make string operations easier and more consistent with standard python string operations.

  • Added StringMethods (.str accessor) to Index (GH9068)

    The .str accessor is now available for both Series and Index.

    In [26]: idx = Index([' jack', 'jill ', ' jesse ', 'frank'])
    In [27]: idx.str.strip()
    Out[27]: Index([u'jack', u'jill', u'jesse', u'frank'], dtype='object')

    One special case for the .str accessor on Index is that if a string method returns bool, the .str accessor will return a np.array instead of a boolean Index (GH8875). This enables the following expression to work naturally:

    In [28]: idx = Index(['a1', 'a2', 'b1', 'b2'])
    In [29]: s = Series(range(4), index=idx)
    In [30]: s
    a1    0
    a2    1
    b1    2
    b2    3
    dtype: int64
    In [31]: idx.str.startswith('a')
    Out[31]: array([ True,  True, False, False], dtype=bool)
    In [32]: s[s.index.str.startswith('a')]
    a1    0
    a2    1
    dtype: int64
  • The following new methods are accesible via .str accessor to apply the function to each values. (GH9766, GH9773, GH10031, GH10045, GH10052)

    capitalize() swapcase() normalize() partition() rpartition()
    index() rindex() translate()    
  • split now takes expand keyword to specify whether to expand dimensionality. return_type is deprecated. (GH9847)

    In [33]: s = Series(['a,b', 'a,c', 'b,c'])
    # return Series
    In [34]: s.str.split(',')
    0    [a, b]
    1    [a, c]
    2    [b, c]
    dtype: object
    # return DataFrame
    In [35]: s.str.split(',', expand=True)
       0  1
    0  a  b
    1  a  c
    2  b  c
    In [36]: idx = Index(['a,b', 'a,c', 'b,c'])
    # return Index
    In [37]: idx.str.split(',')
    Out[37]: Index([[u'a', u'b'], [u'a', u'c'], [u'b', u'c']], dtype='object')
    # return MultiIndex
    In [38]: idx.str.split(',', expand=True)
    MultiIndex(levels=[[u'a', u'b'], [u'b', u'c']],
               labels=[[0, 0, 1], [0, 1, 1]])
  • Improved extract and get_dummies methods for Index.str (GH9980)

Other Enhancements

  • BusinessHour offset is now supported, which represents business hours starting from 09:00 - 17:00 on BusinessDay by default. See Here for details. (GH7905)

    In [39]: from pandas.tseries.offsets import BusinessHour
    In [40]: Timestamp('2014-08-01 09:00') + BusinessHour()
    Out[40]: Timestamp('2014-08-01 10:00:00')
    In [41]: Timestamp('2014-08-01 07:00') + BusinessHour()
    Out[41]: Timestamp('2014-08-01 10:00:00')
    In [42]: Timestamp('2014-08-01 16:30') + BusinessHour()
    Out[42]: Timestamp('2014-08-04 09:30:00')
  • DataFrame.diff now takes an axis parameter that determines the direction of differencing (GH9727)

  • Allow clip, clip_lower, and clip_upper to accept array-like arguments as thresholds (This is a regression from 0.11.0). These methods now have an axis parameter which determines how the Series or DataFrame will be aligned with the threshold(s). (GH6966)

  • DataFrame.mask() and Series.mask() now support same keywords as where (GH8801)

  • drop function can now accept errors keyword to suppress ValueError raised when any of label does not exist in the target data. (GH6736)

    In [43]: df = DataFrame(np.random.randn(3, 3), columns=['A', 'B', 'C'])
    In [44]: df.drop(['A', 'X'], axis=1, errors='ignore')
              B         C
    0  0.991946  0.953324
    1 -0.334077  0.002118
    2  0.289092  1.321158
  • Add support for separating years and quarters using dashes, for example 2014-Q1. (GH9688)

  • Allow conversion of values with dtype datetime64 or timedelta64 to strings using astype(str) (GH9757)

  • get_dummies function now accepts sparse keyword. If set to True, the return DataFrame is sparse, e.g. SparseDataFrame. (GH8823)

  • Period now accepts datetime64 as value input. (GH9054)

  • Allow timedelta string conversion when leading zero is missing from time definition, ie 0:00:00 vs 00:00:00. (GH9570)

  • Allow Panel.shift with axis='items' (GH9890)

  • Trying to write an excel file now raises NotImplementedError if the DataFrame has a MultiIndex instead of writing a broken Excel file. (GH9794)

  • Allow Categorical.add_categories to accept Series or np.array. (GH9927)

  • Add/delete str/dt/cat accessors dynamically from __dir__. (GH9910)

  • Add normalize as a dt accessor method. (GH10047)

  • DataFrame and Series now have _constructor_expanddim property as overridable constructor for one higher dimensionality data. This should be used only when it is really needed, see here

  • pd.lib.infer_dtype now returns 'bytes' in Python 3 where appropriate. (GH10032)

API changes

  • When passing in an ax to df.plot( ..., ax=ax), the sharex kwarg will now default to False. The result is that the visibility of xlabels and xticklabels will not anymore be changed. You have to do that by yourself for the right axes in your figure or set sharex=True explicitly (but this changes the visible for all axes in the figure, not only the one which is passed in!). If pandas creates the subplots itself (e.g. no passed in ax kwarg), then the default is still sharex=True and the visibility changes are applied.
  • assign() now inserts new columns in alphabetical order. Previously the order was arbitrary. (GH9777)
  • By default, read_csv and read_table will now try to infer the compression type based on the file extension. Set compression=None to restore the previous behavior (no decompression). (GH9770)


  • Series.str.split‘s return_type keyword was removed in favor of expand (GH9847)

Index Representation

The string representation of Index and its sub-classes have now been unified. These will show a single-line display if there are few values; a wrapped multi-line display for a lot of values (but less than display.max_seq_items; if lots of items (> display.max_seq_items) will show a truncated display (the head and tail of the data). The formatting for MultiIndex is unchanges (a multi-line wrapped display). The display width responds to the option display.max_seq_items, which is defaulted to 100. (GH6482)

Previous Behavior

In [2]: pd.Index(range(4),name='foo')
Out[2]: Int64Index([0, 1, 2, 3], dtype='int64')

In [3]: pd.Index(range(104),name='foo')
Out[3]: Int64Index([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, ...], dtype='int64')

In [4]: pd.date_range('20130101',periods=4,name='foo',tz='US/Eastern')
<class 'pandas.tseries.index.DatetimeIndex'>
[2013-01-01 00:00:00-05:00, ..., 2013-01-04 00:00:00-05:00]
Length: 4, Freq: D, Timezone: US/Eastern

In [5]: pd.date_range('20130101',periods=104,name='foo',tz='US/Eastern')
<class 'pandas.tseries.index.DatetimeIndex'>
[2013-01-01 00:00:00-05:00, ..., 2013-04-14 00:00:00-04:00]
Length: 104, Freq: D, Timezone: US/Eastern

New Behavior

In [45]: pd.set_option('display.width', 80)

In [46]: pd.Index(range(4), name='foo')
Out[46]: Int64Index([0, 1, 2, 3], dtype='int64', name=u'foo')

In [47]: pd.Index(range(30), name='foo')
Int64Index([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16,
            17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
           dtype='int64', name=u'foo')

In [48]: pd.Index(range(104), name='foo')
Int64Index([  0,   1,   2,   3,   4,   5,   6,   7,   8,   9,
             94,  95,  96,  97,  98,  99, 100, 101, 102, 103],
           dtype='int64', name=u'foo', length=104)

In [49]: pd.CategoricalIndex(['a','bb','ccc','dddd'], ordered=True, name='foobar')
Out[49]: CategoricalIndex([u'a', u'bb', u'ccc', u'dddd'], categories=[u'a', u'bb', u'ccc', u'dddd'], ordered=True, name=u'foobar', dtype='category')

In [50]: pd.CategoricalIndex(['a','bb','ccc','dddd']*10, ordered=True, name='foobar')
CategoricalIndex([u'a', u'bb', u'ccc', u'dddd', u'a', u'bb', u'ccc', u'dddd',
                  u'a', u'bb', u'ccc', u'dddd', u'a', u'bb', u'ccc', u'dddd',
                  u'a', u'bb', u'ccc', u'dddd', u'a', u'bb', u'ccc', u'dddd',
                  u'a', u'bb', u'ccc', u'dddd', u'a', u'bb', u'ccc', u'dddd',
                  u'a', u'bb', u'ccc', u'dddd', u'a', u'bb', u'ccc', u'dddd'],
                 categories=[u'a', u'bb', u'ccc', u'dddd'], ordered=True, name=u'foobar', dtype='category')

In [51]: pd.CategoricalIndex(['a','bb','ccc','dddd']*100, ordered=True, name='foobar')
CategoricalIndex([u'a', u'bb', u'ccc', u'dddd', u'a', u'bb', u'ccc', u'dddd',
                  u'a', u'bb',
                  u'ccc', u'dddd', u'a', u'bb', u'ccc', u'dddd', u'a', u'bb',
                  u'ccc', u'dddd'],
                 categories=[u'a', u'bb', u'ccc', u'dddd'], ordered=True, name=u'foobar', dtype='category', length=400)

In [52]: pd.date_range('20130101',periods=4, name='foo', tz='US/Eastern')
DatetimeIndex(['2013-01-01 00:00:00-05:00', '2013-01-02 00:00:00-05:00',
               '2013-01-03 00:00:00-05:00', '2013-01-04 00:00:00-05:00'],
              dtype='datetime64[ns, US/Eastern]', name=u'foo', freq='D')

In [53]: pd.date_range('20130101',periods=25, freq='D')
DatetimeIndex(['2013-01-01', '2013-01-02', '2013-01-03', '2013-01-04',
               '2013-01-05', '2013-01-06', '2013-01-07', '2013-01-08',
               '2013-01-09', '2013-01-10', '2013-01-11', '2013-01-12',
               '2013-01-13', '2013-01-14', '2013-01-15', '2013-01-16',
               '2013-01-17', '2013-01-18', '2013-01-19', '2013-01-20',
               '2013-01-21', '2013-01-22', '2013-01-23', '2013-01-24',
              dtype='datetime64[ns]', freq='D')

In [54]: pd.date_range('20130101',periods=104, name='foo', tz='US/Eastern')
DatetimeIndex(['2013-01-01 00:00:00-05:00', '2013-01-02 00:00:00-05:00',
               '2013-01-03 00:00:00-05:00', '2013-01-04 00:00:00-05:00',
               '2013-01-05 00:00:00-05:00', '2013-01-06 00:00:00-05:00',
               '2013-01-07 00:00:00-05:00', '2013-01-08 00:00:00-05:00',
               '2013-01-09 00:00:00-05:00', '2013-01-10 00:00:00-05:00',
               '2013-04-05 00:00:00-04:00', '2013-04-06 00:00:00-04:00',
               '2013-04-07 00:00:00-04:00', '2013-04-08 00:00:00-04:00',
               '2013-04-09 00:00:00-04:00', '2013-04-10 00:00:00-04:00',
               '2013-04-11 00:00:00-04:00', '2013-04-12 00:00:00-04:00',
               '2013-04-13 00:00:00-04:00', '2013-04-14 00:00:00-04:00'],
              dtype='datetime64[ns, US/Eastern]', name=u'foo', length=104, freq='D')

Performance Improvements

  • Improved csv write performance with mixed dtypes, including datetimes by up to 5x (GH9940)
  • Improved csv write performance generally by 2x (GH9940)
  • Improved the performance of pd.lib.max_len_string_array by 5-7x (GH10024)

Bug Fixes

  • Bug where labels did not appear properly in the legend of DataFrame.plot(), passing label= arguments works, and Series indices are no longer mutated. (GH9542)
  • Bug in json serialization causing a segfault when a frame had zero length. (GH9805)
  • Bug in read_csv where missing trailing delimiters would cause segfault. (GH5664)
  • Bug in retaining index name on appending (GH9862)
  • Bug in scatter_matrix draws unexpected axis ticklabels (GH5662)
  • Fixed bug in StataWriter resulting in changes to input DataFrame upon save (GH9795).
  • Bug in transform causing length mismatch when null entries were present and a fast aggregator was being used (GH9697)
  • Bug in equals causing false negatives when block order differed (GH9330)
  • Bug in grouping with multiple pd.Grouper where one is non-time based (GH10063)
  • Bug in read_sql_table error when reading postgres table with timezone (GH7139)
  • Bug in DataFrame slicing may not retain metadata (GH9776)
  • Bug where TimdeltaIndex were not properly serialized in fixed HDFStore (GH9635)
  • Bug with TimedeltaIndex constructor ignoring name when given another TimedeltaIndex as data (GH10025).
  • Bug in DataFrameFormatter._get_formatted_index with not applying max_colwidth to the DataFrame index (GH7856)
  • Bug in .loc with a read-only ndarray data source (GH10043)
  • Bug in groupby.apply() that would raise if a passed user defined function either returned only None (for all input). (GH9685)
  • Always use temporary files in pytables tests (GH9992)
  • Bug in plotting continuously using secondary_y may not show legend properly. (GH9610, GH9779)
  • Bug in DataFrame.plot(kind="hist") results in TypeError when DataFrame contains non-numeric columns (GH9853)
  • Bug where repeated plotting of DataFrame with a DatetimeIndex may raise TypeError (GH9852)
  • Bug in that would allow an incompat cython version to build (GH9827)
  • Bug in plotting secondary_y incorrectly attaches right_ax property to secondary axes specifying itself recursively. (GH9861)
  • Bug in Series.quantile on empty Series of type Datetime or Timedelta (GH9675)
  • Bug in where causing incorrect results when upcasting was required (GH9731)
  • Bug in FloatArrayFormatter where decision boundary for displaying “small” floats in decimal format is off by one order of magnitude for a given display.precision (GH9764)
  • Fixed bug where DataFrame.plot() raised an error when both color and style keywords were passed and there was no color symbol in the style strings (GH9671)
  • Not showing a DeprecationWarning on combining list-likes with an Index (GH10083)
  • Bug in read_csv and read_table when using skip_rows parameter if blank lines are present. (GH9832)
  • Bug in read_csv() interprets index_col=True as 1 (GH9798)
  • Bug in index equality comparisons using == failing on Index/MultiIndex type incompatibility (GH9785)
  • Bug in which SparseDataFrame could not take nan as a column name (GH8822)
  • Bug in to_msgpack and read_msgpack zlib and blosc compression support (GH9783)
  • Bug GroupBy.size doesn’t attach index name properly if grouped by TimeGrouper (GH9925)
  • Bug causing an exception in slice assignments because length_of_indexer returns wrong results (GH9995)
  • Bug in csv parser causing lines with initial whitespace plus one non-space character to be skipped. (GH9710)
  • Bug in C csv parser causing spurious NaNs when data started with newline followed by whitespace. (GH10022)
  • Bug causing elements with a null group to spill into the final group when grouping by a Categorical (GH9603)
  • Bug where .iloc and .loc behavior is not consistent on empty dataframes (GH9964)
  • Bug in invalid attribute access on a TimedeltaIndex incorrectly raised ValueError instead of AttributeError (GH9680)
  • Bug in unequal comparisons between categorical data and a scalar, which was not in the categories (e.g. Series(Categorical(list("abc"), ordered=True)) > "d". This returned False for all elements, but now raises a TypeError. Equality comparisons also now return False for == and True for !=. (GH9848)
  • Bug in DataFrame __setitem__ when right hand side is a dictionary (GH9874)
  • Bug in where when dtype is datetime64/timedelta64, but dtype of other is not (GH9804)
  • Bug in MultiIndex.sortlevel() results in unicode level name breaks (GH9856)
  • Bug in which groupby.transform incorrectly enforced output dtypes to match input dtypes. (GH9807)
  • Bug in DataFrame constructor when columns parameter is set, and data is an empty list (GH9939)
  • Bug in bar plot with log=True raises TypeError if all values are less than 1 (GH9905)
  • Bug in horizontal bar plot ignores log=True (GH9905)
  • Bug in PyTables queries that did not return proper results using the index (GH8265, GH9676)
  • Bug where dividing a dataframe containing values of type Decimal by another Decimal would raise. (GH9787)
  • Bug where using DataFrames asfreq would remove the name of the index. (GH9885)
  • Bug causing extra index point when resample BM/BQ (GH9756)
  • Changed caching in AbstractHolidayCalendar to be at the instance level rather than at the class level as the latter can result in unexpected behaviour. (GH9552)
  • Fixed latex output for multi-indexed dataframes (GH9778)
  • Bug causing an exception when setting an empty range using DataFrame.loc (GH9596)
  • Bug in hiding ticklabels with subplots and shared axes when adding a new plot to an existing grid of axes (GH9158)
  • Bug in transform and filter when grouping on a categorical variable (GH9921)
  • Bug in transform when groups are equal in number and dtype to the input index (GH9700)
  • Google BigQuery connector now imports dependencies on a per-method basis.(GH9713)
  • Updated BigQuery connector to no longer use deprecated (GH8327)
  • Bug in subclassed DataFrame. It may not return the correct class, when slicing or subsetting it. (GH9632)
  • Bug in .median() where non-float null values are not handled correctly (GH10040)
  • Bug in Series.fillna() where it raises if a numerically convertible string is given (GH10092)

v0.16.0 (March 22, 2015)

This is a major release from 0.15.2 and includes a small number of API changes, several new features, enhancements, and performance improvements along with a large number of bug fixes. We recommend that all users upgrade to this version.

Highlights include:

  • DataFrame.assign method, see here
  • Series.to_coo/from_coo methods to interact with scipy.sparse, see here
  • Backwards incompatible change to Timedelta to conform the .seconds attribute with datetime.timedelta, see here
  • Changes to the .loc slicing API to conform with the behavior of .ix see here
  • Changes to the default for ordering in the Categorical constructor, see here
  • Enhancement to the .str accessor to make string operations easier, see here
  • The, pandas.sandbox.qtpandas and pandas.rpy modules are deprecated. We refer users to external packages like seaborn, pandas-qt and rpy2 for similar or equivalent functionality, see here

Check the API Changes and deprecations before updating.

New features

DataFrame Assign

Inspired by dplyr’s mutate verb, DataFrame has a new assign() method. The function signature for assign is simply **kwargs. The keys are the column names for the new fields, and the values are either a value to be inserted (for example, a Series or NumPy array), or a function of one argument to be called on the DataFrame. The new values are inserted, and the entire DataFrame (with all original and new columns) is returned.

In [1]: iris = read_csv('data/')

In [2]: iris.head()
   SepalLength  SepalWidth  PetalLength  PetalWidth         Name
0          5.1         3.5          1.4         0.2  Iris-setosa
1          4.9         3.0          1.4         0.2  Iris-setosa
2          4.7         3.2          1.3         0.2  Iris-setosa
3          4.6         3.1          1.5         0.2  Iris-setosa
4          5.0         3.6          1.4         0.2  Iris-setosa

In [3]: iris.assign(sepal_ratio=iris['SepalWidth'] / iris['SepalLength']).head()
   SepalLength  SepalWidth  PetalLength  PetalWidth         Name  sepal_ratio
0          5.1         3.5          1.4         0.2  Iris-setosa     0.686275
1          4.9         3.0          1.4         0.2  Iris-setosa     0.612245
2          4.7         3.2          1.3         0.2  Iris-setosa     0.680851
3          4.6         3.1          1.5         0.2  Iris-setosa     0.673913
4          5.0         3.6          1.4         0.2  Iris-setosa     0.720000

Above was an example of inserting a precomputed value. We can also pass in a function to be evalutated.

In [4]: iris.assign(sepal_ratio = lambda x: (x['SepalWidth'] /
   ...:                                      x['SepalLength'])).head()
   SepalLength  SepalWidth  PetalLength  PetalWidth         Name  sepal_ratio
0          5.1         3.5          1.4         0.2  Iris-setosa     0.686275
1          4.9         3.0          1.4         0.2  Iris-setosa     0.612245
2          4.7         3.2          1.3         0.2  Iris-setosa     0.680851
3          4.6         3.1          1.5         0.2  Iris-setosa     0.673913
4          5.0         3.6          1.4         0.2  Iris-setosa     0.720000

The power of assign comes when used in chains of operations. For example, we can limit the DataFrame to just those with a Sepal Length greater than 5, calculate the ratio, and plot

In [5]: (iris.query('SepalLength > 5')
   ...:      .assign(SepalRatio = lambda x: x.SepalWidth / x.SepalLength,
   ...:              PetalRatio = lambda x: x.PetalWidth / x.PetalLength)
   ...:      .plot(kind='scatter', x='SepalRatio', y='PetalRatio'))
Out[5]: <matplotlib.axes._subplots.AxesSubplot at 0x94922a4c>

See the documentation for more. (GH9229)

Interaction with scipy.sparse

Added SparseSeries.to_coo() and SparseSeries.from_coo() methods (GH8048) for converting to and from scipy.sparse.coo_matrix instances (see here). For example, given a SparseSeries with MultiIndex we can convert to a scipy.sparse.coo_matrix by specifying the row and column labels as index levels:

In [6]: from numpy import nan

In [7]: s = Series([3.0, nan, 1.0, 3.0, nan, nan])

In [8]: s.index = MultiIndex.from_tuples([(1, 2, 'a', 0),
   ...:                                   (1, 2, 'a', 1),
   ...:                                   (1, 1, 'b', 0),
   ...:                                   (1, 1, 'b', 1),
   ...:                                   (2, 1, 'b', 0),
   ...:                                   (2, 1, 'b', 1)],
   ...:                                   names=['A', 'B', 'C', 'D'])

In [9]: s
A  B  C  D
1  2  a  0     3
         1   NaN
   1  b  0     1
         1     3
2  1  b  0   NaN
         1   NaN
dtype: float64

# SparseSeries
In [10]: ss = s.to_sparse()

In [11]: ss
A  B  C  D
1  2  a  0     3
         1   NaN
   1  b  0     1
         1     3
2  1  b  0   NaN
         1   NaN
dtype: float64
Block locations: array([0, 2])
Block lengths: array([1, 2])

In [12]: A, rows, columns = ss.to_coo(row_levels=['A', 'B'],
   ....:                              column_levels=['C', 'D'],
   ....:                              sort_labels=False)

In [13]: A
<3x4 sparse matrix of type '<type 'numpy.float64'>'
	with 3 stored elements in COOrdinate format>

In [14]: A.todense()
matrix([[ 3.,  0.,  0.,  0.],
        [ 0.,  0.,  1.,  3.],
        [ 0.,  0.,  0.,  0.]])

In [15]: rows
Out[15]: [(1L, 2L), (1L, 1L), (2L, 1L)]

In [16]: columns
Out[16]: [('a', 0L), ('a', 1L), ('b', 0L), ('b', 1L)]

The from_coo method is a convenience method for creating a SparseSeries from a scipy.sparse.coo_matrix:

In [17]: from scipy import sparse

In [18]: A = sparse.coo_matrix(([3.0, 1.0, 2.0], ([1, 0, 0], [0, 2, 3])),
   ....:                             shape=(3, 4))

In [19]: A
<3x4 sparse matrix of type '<type 'numpy.float64'>'
	with 3 stored elements in COOrdinate format>

In [20]: A.todense()
matrix([[ 0.,  0.,  1.,  2.],
        [ 3.,  0.,  0.,  0.],
        [ 0.,  0.,  0.,  0.]])

In [21]: ss = SparseSeries.from_coo(A)

In [22]: ss
0  2    1
   3    2
1  0    3
dtype: float64
Block locations: array([0])
Block lengths: array([3])

String Methods Enhancements

  • Following new methods are accesible via .str accessor to apply the function to each values. This is intended to make it more consistent with standard methods on strings. (GH9282, GH9352, GH9386, GH9387, GH9439)

    isalnum() isalpha() isdigit() isdigit() isspace()
    islower() isupper() istitle() isnumeric() isdecimal()
    find() rfind() ljust() rjust() zfill()
    In [23]: s = Series(['abcd', '3456', 'EFGH'])
    In [24]: s.str.isalpha()
    0     True
    1    False
    2     True
    dtype: bool
    In [25]: s.str.find('ab')
    0    0
    1   -1
    2   -1
    dtype: int64
  • Series.str.pad() and now accept fillchar option to specify filling character (GH9352)

    In [26]: s = Series(['12', '300', '25'])
    In [27]: s.str.pad(5, fillchar='_')
    0    ___12
    1    __300
    2    ___25
    dtype: object
  • Added Series.str.slice_replace(), which previously raised NotImplementedError (GH8888)

    In [28]: s = Series(['ABCD', 'EFGH', 'IJK'])
    In [29]: s.str.slice_replace(1, 3, 'X')
    0    AXD
    1    EXH
    2     IX
    dtype: object
    # replaced with empty char
    In [30]: s.str.slice_replace(0, 1)
    0    BCD
    1    FGH
    2     JK
    dtype: object

Other enhancements

  • Reindex now supports method='nearest' for frames or series with a monotonic increasing or decreasing index (GH9258):

    In [31]: df = pd.DataFrame({'x': range(5)})
    In [32]: df.reindex([0.2, 1.8, 3.5], method='nearest')
    0.2  0
    1.8  2
    3.5  4

    This method is also exposed by the lower level Index.get_indexer and Index.get_loc methods.

  • The read_excel() function’s sheetname argument now accepts a list and None, to get multiple or all sheets respectively. If more than one sheet is specified, a dictionary is returned. (GH9450)

    # Returns the 1st and 4th sheet, as a dictionary of DataFrames.
  • Allow Stata files to be read incrementally with an iterator; support for long strings in Stata files. See the docs here (GH9493:).

  • Paths beginning with ~ will now be expanded to begin with the user’s home directory (GH9066)

  • Added time interval selection in get_data_yahoo (GH9071)

  • Added Timestamp.to_datetime64() to complement Timedelta.to_timedelta64() (GH9255)

  • tseries.frequencies.to_offset() now accepts Timedelta as input (GH9064)

  • Lag parameter was added to the autocorrelation method of Series, defaults to lag-1 autocorrelation (GH9192)

  • Timedelta will now accept nanoseconds keyword in constructor (GH9273)

  • SQL code now safely escapes table and column names (GH8986)

  • Added auto-complete for Series.str.<tab>, Series.dt.<tab> and<tab> (GH9322)

  • Index.get_indexer now supports method='pad' and method='backfill' even for any target array, not just monotonic targets. These methods also work for monotonic decreasing as well as monotonic increasing indexes (GH9258).

  • Index.asof now works on all index types (GH9258).

  • A verbose argument has been augmented in io.read_excel(), defaults to False. Set to True to print sheet names as they are parsed. (GH9450)

  • Added days_in_month (compatibility alias daysinmonth) property to Timestamp, DatetimeIndex, Period, PeriodIndex, and Series.dt (GH9572)

  • Added decimal option in to_csv to provide formatting for non-‘.’ decimal separators (GH781)

  • Added normalize option for Timestamp to normalized to midnight (GH8794)

  • Added example for DataFrame import to R using HDF5 file and rhdf5 library. See the documentation for more (GH9636).

Backwards incompatible API changes

Changes in Timedelta

In v0.15.0 a new scalar type Timedelta was introduced, that is a sub-class of datetime.timedelta. Mentioned here was a notice of an API change w.r.t. the .seconds accessor. The intent was to provide a user-friendly set of accessors that give the ‘natural’ value for that unit, e.g. if you had a Timedelta('1 day, 10:11:12'), then .seconds would return 12. However, this is at odds with the definition of datetime.timedelta, which defines .seconds as 10 * 3600 + 11 * 60 + 12 == 36672.

So in v0.16.0, we are restoring the API to match that of datetime.timedelta. Further, the component values are still available through the .components accessor. This affects the .seconds and .microseconds accessors, and removes the .hours, .minutes, .milliseconds accessors. These changes affect TimedeltaIndex and the Series .dt accessor as well. (GH9185, GH9139)

Previous Behavior

In [2]: t = pd.Timedelta('1 day, 10:11:12.100123')

In [3]: t.days
Out[3]: 1

In [4]: t.seconds
Out[4]: 12

In [5]: t.microseconds
Out[5]: 123

New Behavior

In [33]: t = pd.Timedelta('1 day, 10:11:12.100123')

In [34]: t.days
Out[34]: 1L

In [35]: t.seconds
Out[35]: 36672L

In [36]: t.microseconds
Out[36]: 100123L

Using .components allows the full component access

In [37]: t.components
Out[37]: Components(days=1L, hours=10L, minutes=11L, seconds=12L, milliseconds=100L, microseconds=123L, nanoseconds=0L)

In [38]: t.components.seconds
Out[38]: 12L

Indexing Changes

The behavior of a small sub-set of edge cases for using .loc have changed (GH8613). Furthermore we have improved the content of the error messages that are raised:

  • Slicing with .loc where the start and/or stop bound is not found in the index is now allowed; this previously would raise a KeyError. This makes the behavior the same as .ix in this case. This change is only for slicing, not when indexing with a single label.

    In [39]: df = DataFrame(np.random.randn(5,4),
       ....:                columns=list('ABCD'),
       ....:                index=date_range('20130101',periods=5))
    In [40]: df
                       A         B         C         D
    2013-01-01 -1.546906 -0.202646 -0.655969  0.193421
    2013-01-02  0.553439  1.318152 -0.469305  0.675554
    2013-01-03 -1.817027 -0.183109  1.058969 -0.397840
    2013-01-04  0.337438  1.047579  1.045938  0.863717
    2013-01-05 -0.122092  0.124713 -0.322795  0.841675
    In [41]: s = Series(range(5),[-2,-1,1,2,3])
    In [42]: s
    -2    0
    -1    1
     1    2
     2    3
     3    4
    dtype: int64

    Previous Behavior

    In [4]: df.loc['2013-01-02':'2013-01-10']
    KeyError: 'stop bound [2013-01-10] is not in the [index]'
    In [6]: s.loc[-10:3]
    KeyError: 'start bound [-10] is not the [index]'

    New Behavior

    In [43]: df.loc['2013-01-02':'2013-01-10']
                       A         B         C         D
    2013-01-02  0.553439  1.318152 -0.469305  0.675554
    2013-01-03 -1.817027 -0.183109  1.058969 -0.397840
    2013-01-04  0.337438  1.047579  1.045938  0.863717
    2013-01-05 -0.122092  0.124713 -0.322795  0.841675
    In [44]: s.loc[-10:3]
    -2    0
    -1    1
     1    2
     2    3
     3    4
    dtype: int64
  • Allow slicing with float-like values on an integer index for .ix. Previously this was only enabled for .loc:

    Previous Behavior

    In [8]: s.ix[-1.0:2]
    TypeError: the slice start value [-1.0] is not a proper indexer for this index type (Int64Index)

    New Behavior

    In [45]: s.ix[-1.0:2]
    -1    1
     1    2
     2    3
    dtype: int64
  • Provide a useful exception for indexing with an invalid type for that index when using .loc. For example trying to use .loc on an index of type DatetimeIndex or PeriodIndex or TimedeltaIndex, with an integer (or a float).

    Previous Behavior

    In [4]: df.loc[2:3]
    KeyError: 'start bound [2] is not the [index]'

    New Behavior

    In [4]: df.loc[2:3]
    TypeError: Cannot do slice indexing on <class 'pandas.tseries.index.DatetimeIndex'> with <type 'int'> keys

Categorical Changes

In prior versions, Categoricals that had an unspecified ordering (meaning no ordered keyword was passed) were defaulted as ordered Categoricals. Going forward, the ordered keyword in the Categorical constructor will default to False. Ordering must now be explicit.

Furthermore, previously you could change the ordered attribute of a Categorical by just setting the attribute, e.g. cat.ordered=True; This is now deprecated and you should use cat.as_ordered() or cat.as_unordered(). These will by default return a new object and not modify the existing object. (GH9347, GH9190)

Previous Behavior

In [3]: s = Series([0,1,2], dtype='category')

In [4]: s
0    0
1    1
2    2
dtype: category
Categories (3, int64): [0 < 1 < 2]

In [5]:
Out[5]: True

In [6]: = False

In [7]: s
0    0
1    1
2    2
dtype: category
Categories (3, int64): [0, 1, 2]

New Behavior

In [46]: s = Series([0,1,2], dtype='category')

In [47]: s
0    0
1    1
2    2
dtype: category
Categories (3, int64): [0, 1, 2]

In [48]:
Out[48]: False

In [49]: s =

In [50]: s
0    0
1    1
2    2
dtype: category
Categories (3, int64): [0 < 1 < 2]

In [51]:
Out[51]: True

# you can set in the constructor of the Categorical
In [52]: s = Series(Categorical([0,1,2],ordered=True))

In [53]: s
0    0
1    1
2    2
dtype: category
Categories (3, int64): [0 < 1 < 2]

In [54]:
Out[54]: True

For ease of creation of series of categorical data, we have added the ability to pass keywords when calling .astype(). These are passed directly to the constructor.

In [55]: s = Series(["a","b","c","a"]).astype('category',ordered=True)

In [56]: s
0    a
1    b
2    c
3    a
dtype: category
Categories (3, object): [a < b < c]

In [57]: s = Series(["a","b","c","a"]).astype('category',categories=list('abcdef'),ordered=False)

In [58]: s
0    a
1    b
2    c
3    a
dtype: category
Categories (6, object): [a, b, c, d, e, f]

Other API Changes

  • Index.duplicated now returns np.array(dtype=bool) rather than Index(dtype=object) containing bool values. (GH8875)

  • DataFrame.to_json now returns accurate type serialisation for each column for frames of mixed dtype (GH9037)

    Previously data was coerced to a common dtype before serialisation, which for example resulted in integers being serialised to floats:

    In [2]: pd.DataFrame({'i': [1,2], 'f': [3.0, 4.2]}).to_json()
    Out[2]: '{"f":{"0":3.0,"1":4.2},"i":{"0":1.0,"1":2.0}}'

    Now each column is serialised using its correct dtype:

    In [2]:  pd.DataFrame({'i': [1,2], 'f': [3.0, 4.2]}).to_json()
    Out[2]: '{"f":{"0":3.0,"1":4.2},"i":{"0":1,"1":2}}'
  • DatetimeIndex, PeriodIndex and TimedeltaIndex.summary now output the same format. (GH9116)

  • TimedeltaIndex.freqstr now output the same string format as DatetimeIndex. (GH9116)

  • Bar and horizontal bar plots no longer add a dashed line along the info axis. The prior style can be achieved with matplotlib’s axhline or axvline methods (GH9088).

  • Series accessors .dt, .cat and .str now raise AttributeError instead of TypeError if the series does not contain the appropriate type of data (GH9617). This follows Python’s built-in exception hierarchy more closely and ensures that tests like hasattr(s, 'cat') are consistent on both Python 2 and 3.

  • Series now supports bitwise operation for integral types (GH9016). Previously even if the input dtypes were integral, the output dtype was coerced to bool.

    Previous Behavior

    In [2]: pd.Series([0,1,2,3], list('abcd')) | pd.Series([4,4,4,4], list('abcd'))
    a    True
    b    True
    c    True
    d    True
    dtype: bool

    New Behavior. If the input dtypes are integral, the output dtype is also integral and the output values are the result of the bitwise operation.

    In [2]: pd.Series([0,1,2,3], list('abcd')) | pd.Series([4,4,4,4], list('abcd'))
    a    4
    b    5
    c    6
    d    7
    dtype: int64
  • During division involving a Series or DataFrame, 0/0 and 0//0 now give np.nan instead of np.inf. (GH9144, GH8445)

    Previous Behavior

    In [2]: p = pd.Series([0, 1])
    In [3]: p / 0
    0    inf
    1    inf
    dtype: float64
    In [4]: p // 0
    0    inf
    1    inf
    dtype: float64

    New Behavior

    In [59]: p = pd.Series([0, 1])
    In [60]: p / 0
    0    NaN
    1    inf
    dtype: float64
    In [61]: p // 0
    0    NaN
    1    inf
    dtype: float64
  • Series.values_counts and Series.describe for categorical data will now put NaN entries at the end. (GH9443)

  • Series.describe for categorical data will now give counts and frequencies of 0, not NaN, for unused categories (GH9443)

  • Due to a bug fix, looking up a partial string label with DatetimeIndex.asof now includes values that match the string, even if they are after the start of the partial string label (GH9258).

    Old behavior:

    In [4]: pd.to_datetime(['2000-01-31', '2000-02-28']).asof('2000-02')
    Out[4]: Timestamp('2000-01-31 00:00:00')

    Fixed behavior:

    In [62]: pd.to_datetime(['2000-01-31', '2000-02-28']).asof('2000-02')
    Out[62]: Timestamp('2000-02-28 00:00:00')

    To reproduce the old behavior, simply add more precision to the label (e.g., use 2000-02-01 instead of 2000-02).


  • The rplot trellis plotting interface is deprecated and will be removed in a future version. We refer to external packages like seaborn for similar but more refined functionality (GH3445). The documentation includes some examples how to convert your existing code using rplot to seaborn: rplot docs.
  • The pandas.sandbox.qtpandas interface is deprecated and will be removed in a future version. We refer users to the external package pandas-qt. (GH9615)
  • The pandas.rpy interface is deprecated and will be removed in a future version. Similar functionaility can be accessed thru the rpy2 project (GH9602)
  • Adding DatetimeIndex/PeriodIndex to another DatetimeIndex/PeriodIndex is being deprecated as a set-operation. This will be changed to a TypeError in a future version. .union() should be used for the union set operation. (GH9094)
  • Subtracting DatetimeIndex/PeriodIndex from another DatetimeIndex/PeriodIndex is being deprecated as a set-operation. This will be changed to an actual numeric subtraction yielding a TimeDeltaIndex in a future version. .difference() should be used for the differencing set operation. (GH9094)

Removal of prior version deprecations/changes

  • DataFrame.pivot_table and crosstab‘s rows and cols keyword arguments were removed in favor of index and columns (GH6581)
  • DataFrame.to_excel and DataFrame.to_csv cols keyword argument was removed in favor of columns (GH6581)
  • Removed convert_dummies in favor of get_dummies (GH6581)
  • Removed value_range in favor of describe (GH6581)

Performance Improvements

  • Fixed a performance regression for .loc indexing with an array or list-like (GH9126:).
  • DataFrame.to_json 30x performance improvement for mixed dtype frames. (GH9037)
  • Performance improvements in MultiIndex.duplicated by working with labels instead of values (GH9125)
  • Improved the speed of nunique by calling unique instead of value_counts (GH9129, GH7771)
  • Performance improvement of up to 10x in DataFrame.count and DataFrame.dropna by taking advantage of homogeneous/heterogeneous dtypes appropriately (GH9136)
  • Performance improvement of up to 20x in DataFrame.count when using a MultiIndex and the level keyword argument (GH9163)
  • Performance and memory usage improvements in merge when key space exceeds int64 bounds (GH9151)
  • Performance improvements in multi-key groupby (GH9429)
  • Performance improvements in MultiIndex.sortlevel (GH9445)
  • Performance and memory usage improvements in DataFrame.duplicated (GH9398)
  • Cythonized Period (GH9440)
  • Decreased memory usage on to_hdf (GH9648)

Bug Fixes

  • Changed .to_html to remove leading/trailing spaces in table body (GH4987)
  • Fixed issue using read_csv on s3 with Python 3 (GH9452)
  • Fixed compatibility issue in DatetimeIndex affecting architectures where numpy.int_ defaults to numpy.int32 (GH8943)
  • Bug in Panel indexing with an object-like (GH9140)
  • Bug in the returned Series.dt.components index was reset to the default index (GH9247)
  • Bug in Categorical.__getitem__/__setitem__ with listlike input getting incorrect results from indexer coercion (GH9469)
  • Bug in partial setting with a DatetimeIndex (GH9478)
  • Bug in groupby for integer and datetime64 columns when applying an aggregator that caused the value to be changed when the number was sufficiently large (GH9311, GH6620)
  • Fixed bug in to_sql when mapping a Timestamp object column (datetime column with timezone info) to the appropriate sqlalchemy type (GH9085).
  • Fixed bug in to_sql dtype argument not accepting an instantiated SQLAlchemy type (GH9083).
  • Bug in .loc partial setting with a np.datetime64 (GH9516)
  • Incorrect dtypes inferred on datetimelike looking Series & on .xs slices (GH9477)
  • Items in Categorical.unique() (and s.unique() if s is of dtype category) now appear in the order in which they are originally found, not in sorted order (GH9331). This is now consistent with the behavior for other dtypes in pandas.
  • Fixed bug on big endian platforms which produced incorrect results in StataReader (GH8688).
  • Bug in MultiIndex.has_duplicates when having many levels causes an indexer overflow (GH9075, GH5873)
  • Bug in pivot and unstack where nan values would break index alignment (GH4862, GH7401, GH7403, GH7405, GH7466, GH9497)
  • Bug in left join on multi-index with sort=True or null values (GH9210).
  • Bug in MultiIndex where inserting new keys would fail (GH9250).
  • Bug in groupby when key space exceeds int64 bounds (GH9096).
  • Bug in unstack with TimedeltaIndex or DatetimeIndex and nulls (GH9491).
  • Bug in rank where comparing floats with tolerance will cause inconsistent behaviour (GH8365).
  • Fixed character encoding bug in read_stata and StataReader when loading data from a URL (GH9231).
  • Bug in adding offsets.Nano to other offets raises TypeError (GH9284)
  • Bug in DatetimeIndex iteration, related to (GH8890), fixed in (GH9100)
  • Bugs in resample around DST transitions. This required fixing offset classes so they behave correctly on DST transitions. (GH5172, GH8744, GH8653, GH9173, GH9468).
  • Bug in binary operator method (eg .mul()) alignment with integer levels (GH9463).
  • Bug in boxplot, scatter and hexbin plot may show an unnecessary warning (GH8877)
  • Bug in subplot with layout kw may show unnecessary warning (GH9464)
  • Bug in using grouper functions that need passed thru arguments (e.g. axis), when using wrapped function (e.g. fillna), (GH9221)
  • DataFrame now properly supports simultaneous copy and dtype arguments in constructor (GH9099)
  • Bug in read_csv when using skiprows on a file with CR line endings with the c engine. (GH9079)
  • isnull now detects NaT in PeriodIndex (GH9129)
  • Bug in groupby .nth() with a multiple column groupby (GH8979)
  • Bug in DataFrame.where and Series.where coerce numerics to string incorrectly (GH9280)
  • Bug in DataFrame.where and Series.where raise ValueError when string list-like is passed. (GH9280)
  • Accessing Series.str methods on with non-string values now raises TypeError instead of producing incorrect results (GH9184)
  • Bug in DatetimeIndex.__contains__ when index has duplicates and is not monotonic increasing (GH9512)
  • Fixed division by zero error for Series.kurt() when all values are equal (GH9197)
  • Fixed issue in the xlsxwriter engine where it added a default ‘General’ format to cells if no other format wass applied. This prevented other row or column formatting being applied. (GH9167)
  • Fixes issue with index_col=False when usecols is also specified in read_csv. (GH9082)
  • Bug where wide_to_long would modify the input stubnames list (GH9204)
  • Bug in to_sql not storing float64 values using double precision. (GH9009)
  • SparseSeries and SparsePanel now accept zero argument constructors (same as their non-sparse counterparts) (GH9272).
  • Regression in merging Categorical and object dtypes (GH9426)
  • Bug in read_csv with buffer overflows with certain malformed input files (GH9205)
  • Bug in groupby MultiIndex with missing pair (GH9049, GH9344)
  • Fixed bug in Series.groupby where grouping on MultiIndex levels would ignore the sort argument (GH9444)
  • Fix bug in DataFrame.Groupby where sort=False is ignored in the case of Categorical columns. (GH8868)
  • Fixed bug with reading CSV files from Amazon S3 on python 3 raising a TypeError (GH9452)
  • Bug in the Google BigQuery reader where the ‘jobComplete’ key may be present but False in the query results (GH8728)
  • Bug in Series.values_counts with excluding NaN for categorical type Series with dropna=True (GH9443)
  • Fixed mising numeric_only option for DataFrame.std/var/sem (GH9201)
  • Support constructing Panel or Panel4D with scalar data (GH8285)
  • Series text representation disconnected from max_rows/max_columns (GH7508).

  • Series number formatting inconsistent when truncated (GH8532).

    Previous Behavior

    In [2]: pd.options.display.max_rows = 10
    In [3]: s = pd.Series([1,1,1,1,1,1,1,1,1,1,0.9999,1,1]*10)
    In [4]: s
    0    1
    1    1
    2    1
    127    0.9999
    128    1.0000
    129    1.0000
    Length: 130, dtype: float64

    New Behavior

    0      1.0000
    1      1.0000
    2      1.0000
    3      1.0000
    4      1.0000
    125    1.0000
    126    1.0000
    127    0.9999
    128    1.0000
    129    1.0000
    dtype: float64
  • A Spurious SettingWithCopy Warning was generated when setting a new item in a frame in some cases (GH8730)

    The following would previously report a SettingWithCopy Warning.

    In [1]: df1 = DataFrame({'x': Series(['a','b','c']), 'y': Series(['d','e','f'])})
    In [2]: df2 = df1[['x']]
    In [3]: df2['y'] = ['g', 'h', 'i']

v0.15.2 (December 12, 2014)

This is a minor release from 0.15.1 and includes a large number of bug fixes along with several new features, enhancements, and performance improvements. A small number of API changes were necessary to fix existing bugs. We recommend that all users upgrade to this version.

API changes

  • Indexing in MultiIndex beyond lex-sort depth is now supported, though a lexically sorted index will have a better performance. (GH2646)

    In [1]: df = pd.DataFrame({'jim':[0, 0, 1, 1],
       ...:                    'joe':['x', 'x', 'z', 'y'],
       ...:                    'jolie':np.random.rand(4)}).set_index(['jim', 'joe'])
    In [2]: df
    jim joe          
    0   x    0.043324
        x    0.561433
    1   z    0.329668
        y    0.502967
    In [3]: df.index.lexsort_depth
    Out[3]: 1
    # in prior versions this would raise a KeyError
    # will now show a PerformanceWarning
    In [4]: df.loc[(1, 'z')]
    jim joe          
    1   z    0.329668
    # lexically sorting
    In [5]: df2 = df.sortlevel()
    In [6]: df2
    jim joe          
    0   x    0.043324
        x    0.561433
    1   y    0.502967
        z    0.329668
    In [7]: df2.index.lexsort_depth
    Out[7]: 2
    In [8]: df2.loc[(1,'z')]
    jim joe          
    1   z    0.329668
  • Bug in unique of Series with category dtype, which returned all categories regardless whether they were “used” or not (see GH8559 for the discussion). Previous behaviour was to return all categories:

    In [3]: cat = pd.Categorical(['a', 'b', 'a'], categories=['a', 'b', 'c'])
    In [4]: cat
    [a, b, a]
    Categories (3, object): [a < b < c]
    In [5]: cat.unique()
    Out[5]: array(['a', 'b', 'c'], dtype=object)

    Now, only the categories that do effectively occur in the array are returned:

    In [9]: cat = pd.Categorical(['a', 'b', 'a'], categories=['a', 'b', 'c'])
    In [10]: cat.unique()
    [a, b]
    Categories (2, object): [a, b]
  • Series.all and Series.any now support the level and skipna parameters. Series.all, Series.any, Index.all, and Index.any no longer support the out and keepdims parameters, which existed for compatibility with ndarray. Various index types no longer support the all and any aggregation functions and will now raise TypeError. (GH8302).

  • Allow equality comparisons of Series with a categorical dtype and object dtype; previously these would raise TypeError (GH8938)

  • Bug in NDFrame: conflicting attribute/column names now behave consistently between getting and setting. Previously, when both a column and attribute named y existed, data.y would return the attribute, while data.y = z would update the column (GH8994)

    In [11]: data = pd.DataFrame({'x':[1, 2, 3]})
    In [12]: data.y = 2
    In [13]: data['y'] = [2, 4, 6]
    In [14]: data
       x  y
    0  1  2
    1  2  4
    2  3  6
    # this assignment was inconsistent
    In [15]: data.y = 5

    Old behavior:

    In [6]: data.y
    Out[6]: 2
    In [7]: data['y'].values
    Out[7]: array([5, 5, 5])

    New behavior:

    In [16]: data.y
    Out[16]: 5
    In [17]: data['y'].values
    Out[17]: array([2, 4, 6], dtype=int64)
  • Timestamp('now') is now equivalent to in that it returns the local time rather than UTC. Also, Timestamp('today') is now equivalent to and both have tz as a possible argument. (GH9000)

  • Fix negative step support for label-based slices (GH8753)

    Old behavior:

    In [1]: s = pd.Series(np.arange(3), ['a', 'b', 'c'])
    a    0
    b    1
    c    2
    dtype: int64
    In [2]: s.loc['c':'a':-1]
    c    2
    dtype: int64

    New behavior:

    In [18]: s = pd.Series(np.arange(3), ['a', 'b', 'c'])
    In [19]: s.loc['c':'a':-1]
    c    2
    b    1
    a    0
    dtype: int32


Categorical enhancements:

  • Added ability to export Categorical data to Stata (GH8633). See here for limitations of categorical variables exported to Stata data files.
  • Added flag order_categoricals to StataReader and read_stata to select whether to order imported categorical data (GH8836). See here for more information on importing categorical variables from Stata data files.
  • Added ability to export Categorical data to to/from HDF5 (GH7621). Queries work the same as if it was an object array. However, the category dtyped data is stored in a more efficient manner. See here for an example and caveats w.r.t. prior versions of pandas.
  • Added support for searchsorted() on Categorical class (GH8420).

Other enhancements:

  • Added the ability to specify the SQL type of columns when writing a DataFrame to a database (GH8778). For example, specifying to use the sqlalchemy String type instead of the default Text type for string columns:

    from sqlalchemy.types import String
    data.to_sql('data_dtype', engine, dtype={'Col_1': String})
  • Series.all and Series.any now support the level and skipna parameters (GH8302):

    In [20]: s = pd.Series([False, True, False], index=[0, 0, 1])
    In [21]: s.any(level=0)
    0     True
    1    False
    dtype: bool
  • Panel now supports the all and any aggregation functions. (GH8302):

    In [22]: p = pd.Panel(np.random.rand(2, 5, 4) > 0.1)
    In [23]: p.all()
           0      1
    0   True  False
    1   True   True
    2   True   True
    3  False   True
  • Added support for utcfromtimestamp(), fromtimestamp(), and combine() on Timestamp class (GH5351).

  • Added Google Analytics ( basic documentation (GH8835). See here.

  • Timedelta arithmetic returns NotImplemented in unknown cases, allowing extensions by custom classes (GH8813).

  • Timedelta now supports arithemtic with numpy.ndarray objects of the appropriate dtype (numpy 1.8 or newer only) (GH8884).

  • Added Timedelta.to_timedelta64() method to the public API (GH8884).

  • Added gbq.generate_bq_schema() function to the gbq module (GH8325).

  • Series now works with map objects the same way as generators (GH8909).

  • Added context manager to HDFStore for automatic closing (GH8791).

  • to_datetime gains an exact keyword to allow for a format to not require an exact match for a provided format string (if its False). exact defaults to True (meaning that exact matching is still the default) (GH8904)

  • Added axvlines boolean option to parallel_coordinates plot function, determines whether vertical lines will be printed, default is True

  • Added ability to read table footers to read_html (GH8552)

  • to_sql now infers datatypes of non-NA values for columns that contain NA values and have dtype object (GH8778).


  • Reduce memory usage when skiprows is an integer in read_csv (GH8681)
  • Performance boost for to_datetime conversions with a passed format=, and the exact=False (GH8904)

Bug Fixes

  • Bug in concat of Series with category dtype which were coercing to object. (GH8641)
  • Bug in Timestamp-Timestamp not returning a Timedelta type and datelike-datelike ops with timezones (GH8865)
  • Made consistent a timezone mismatch exception (either tz operated with None or incompatible timezone), will now return TypeError rather than ValueError (a couple of edge cases only), (GH8865)
  • Bug in using a pd.Grouper(key=...) with no level/axis or level only (GH8795, GH8866)
  • Report a TypeError when invalid/no paramaters are passed in a groupby (GH8015)
  • Bug in packaging pandas with py2app/cx_Freeze (GH8602, GH8831)
  • Bug in groupby signatures that didn’t include *args or **kwargs (GH8733).
  • now raises RemoteDataError when no expiry dates are available from Yahoo and when it receives no data from Yahoo (GH8761), (GH8783).
  • Unclear error message in csv parsing when passing dtype and names and the parsed data is a different data type (GH8833)
  • Bug in slicing a multi-index with an empty list and at least one boolean indexer (GH8781)
  • now raises RemoteDataError when no expiry dates are available from Yahoo (GH8761).
  • Timedelta kwargs may now be numpy ints and floats (GH8757).
  • Fixed several outstanding bugs for Timedelta arithmetic and comparisons (GH8813, GH5963, GH5436).
  • sql_schema now generates dialect appropriate CREATE TABLE statements (GH8697)
  • slice string method now takes step into account (GH8754)
  • Bug in BlockManager where setting values with different type would break block integrity (GH8850)
  • Bug in DatetimeIndex when using time object as key (GH8667)
  • Bug in merge where how='left' and sort=False would not preserve left frame order (GH7331)
  • Bug in MultiIndex.reindex where reindexing at level would not reorder labels (GH4088)
  • Bug in certain operations with dateutil timezones, manifesting with dateutil 2.3 (GH8639)
  • Regression in DatetimeIndex iteration with a Fixed/Local offset timezone (GH8890)
  • Bug in to_datetime when parsing a nanoseconds using the %f format (GH8989)
  • now raises RemoteDataError when no expiry dates are available from Yahoo and when it receives no data from Yahoo (GH8761), (GH8783).
  • Fix: The font size was only set on x axis if vertical or the y axis if horizontal. (GH8765)
  • Fixed division by 0 when reading big csv files in python 3 (GH8621)
  • Bug in outputing a Multindex with to_html,index=False which would add an extra column (GH8452)
  • Imported categorical variables from Stata files retain the ordinal information in the underlying data (GH8836).
  • Defined .size attribute across NDFrame objects to provide compat with numpy >= 1.9.1; buggy with np.array_split (GH8846)
  • Skip testing of histogram plots for matplotlib <= 1.2 (GH8648).
  • Bug where get_data_google returned object dtypes (GH3995)
  • Bug in DataFrame.stack(..., dropna=False) when the DataFrame’s columns is a MultiIndex whose labels do not reference all its levels. (GH8844)
  • Bug in that Option context applied on __enter__ (GH8514)
  • Bug in resample that causes a ValueError when resampling across multiple days and the last offset is not calculated from the start of the range (GH8683)
  • Bug where DataFrame.plot(kind='scatter') fails when checking if an np.array is in the DataFrame (GH8852)
  • Bug in pd.infer_freq/DataFrame.inferred_freq that prevented proper sub-daily frequency inference when the index contained DST days (GH8772).
  • Bug where index name was still used when plotting a series with use_index=False (GH8558).
  • Bugs when trying to stack multiple columns, when some (or all) of the level names are numbers (GH8584).
  • Bug in MultiIndex where __contains__ returns wrong result if index is not lexically sorted or unique (GH7724)
  • BUG CSV: fix problem with trailing whitespace in skipped rows, (GH8679), (GH8661), (GH8983)
  • Regression in Timestamp does not parse ‘Z’ zone designator for UTC (GH8771)
  • Bug in StataWriter the produces writes strings with 244 characters irrespective of actual size (GH8969)
  • Fixed ValueError raised by cummin/cummax when datetime64 Series contains NaT. (GH8965)
  • Bug in Datareader returns object dtype if there are missing values (GH8980)
  • Bug in plotting if sharex was enabled and index was a timeseries, would show labels on multiple axes (GH3964).
  • Bug where passing a unit to the TimedeltaIndex constructor applied the to nano-second conversion twice. (GH9011).
  • Bug in plotting of a period-like array (GH9012)

v0.15.1 (November 9, 2014)

This is a minor bug-fix release from 0.15.0 and includes a small number of API changes, several new features, enhancements, and performance improvements along with a large number of bug fixes. We recommend that all users upgrade to this version.

API changes

  • s.dt.hour and other .dt accessors will now return np.nan for missing values (rather than previously -1), (GH8689)

    In [1]: s = Series(date_range('20130101',periods=5,freq='D'))
    In [2]: s.iloc[2] = np.nan
    In [3]: s
    0   2013-01-01
    1   2013-01-02
    2          NaT
    3   2013-01-04
    4   2013-01-05
    dtype: datetime64[ns]

    previous behavior:

    In [6]: s.dt.hour
    0    0
    1    0
    2   -1
    3    0
    4    0
    dtype: int64

    current behavior:

    In [4]: s.dt.hour
    0     0
    1     0
    2   NaN
    3     0
    4     0
    dtype: float64
  • groupby with as_index=False will not add erroneous extra columns to result (GH8582):

    In [5]: np.random.seed(2718281)
    In [6]: df = pd.DataFrame(np.random.randint(0, 100, (10, 2)),
       ...:                   columns=['jim', 'joe'])
    In [7]: df.head()
       jim  joe
    0   61   81
    1   96   49
    2   55   65
    3   72   51
    4   77   12
    In [8]: ts = pd.Series(5 * np.random.randint(0, 3, 10))

    previous behavior:

    In [4]: df.groupby(ts, as_index=False).max()
       NaN  jim  joe
    0    0   72   83
    1    5   77   84
    2   10   96   65

    current behavior:

    In [9]: df.groupby(ts, as_index=False).max()
       jim  joe
    0   72   83
    1   77   84
    2   96   65
  • groupby will not erroneously exclude columns if the column name conflics with the grouper name (GH8112):

    In [10]: df = pd.DataFrame({'jim': range(5), 'joe': range(5, 10)})
    In [11]: df
       jim  joe
    0    0    5
    1    1    6
    2    2    7
    3    3    8
    4    4    9
    In [12]: gr = df.groupby(df['jim'] < 2)

    previous behavior (excludes 1st column from output):

    In [4]: gr.apply(sum)
    False   24
    True    11

    current behavior:

    In [13]: gr.apply(sum)
           jim  joe
    False    9   24
    True     1   11
  • Support for slicing with monotonic decreasing indexes, even if start or stop is not found in the index (GH7860):

    In [14]: s = pd.Series(['a', 'b', 'c', 'd'], [4, 3, 2, 1])
    In [15]: s
    4    a
    3    b
    2    c
    1    d
    dtype: object

    previous behavior:

    In [8]: s.loc[3.5:1.5]
    KeyError: 3.5

    current behavior:

    In [16]: s.loc[3.5:1.5]
    3    b
    2    c
    dtype: object
  • has been fixed for a change in the format of the Yahoo Options page (GH8612), (GH8741)


    As a result of a change in Yahoo’s option page layout, when an expiry date is given, Options methods now return data for a single expiry date. Previously, methods returned all data for the selected month.

    The month and year parameters have been undeprecated and can be used to get all options data for a given month.

    If an expiry date that is not valid is given, data for the next expiry after the given date is returned.

    Option data frames are now saved on the instance as callsYYMMDD or putsYYMMDD. Previously they were saved as callsMMYY and putsMMYY. The next expiry is saved as calls and puts.

    New features:

    • The expiry parameter can now be a single date or a list-like object containing dates.
    • A new property expiry_dates was added, which returns all available expiry dates.

    Current behavior:

    In [17]: from import Options
    In [18]: aapl = Options('aapl','yahoo')
    In [19]: aapl.get_call_data().iloc[0:5,0:1]
    Strike Expiry     Type Symbol                    
    80     2015-11-27 call AAPL151127C00080000  34.16
    90     2015-11-27 call AAPL151127C00090000  32.39
    95     2015-11-27 call AAPL151127C00095000  21.45
    96     2015-11-27 call AAPL151127C00096000  26.42
    97     2015-11-27 call AAPL151127C00097000  21.90
    In [20]: aapl.expiry_dates
    [, 11, 27),, 12, 4),, 12, 11),, 12, 18),, 12, 24),, 12, 31),, 1, 15),, 2, 19),, 4, 15),, 6, 17),, 7, 15),, 1, 20),, 1, 19)]
    In [21]: aapl.get_near_stock_price(expiry=aapl.expiry_dates[0:3]).iloc[0:5,0:1]
    Strike Expiry     Type Symbol                   
    119    2015-12-04 call AAPL151204C00119000  1.95
           2015-12-11 call AAPL151211C00119000  2.50
    120    2015-11-27 call AAPL151127C00120000  0.78
           2015-12-04 call AAPL151204C00120000  1.47
           2015-12-11 call AAPL151211C00120000  2.00

    See the Options documentation in Remote Data

  • pandas now also registers the datetime64 dtype in matplotlib’s units registry to plot such values as datetimes. This is activated once pandas is imported. In previous versions, plotting an array of datetime64 values will have resulted in plotted integer values. To keep the previous behaviour, you can do del matplotlib.units.registry[np.datetime64] (GH8614).


  • concat permits a wider variety of iterables of pandas objects to be passed as the first parameter (GH8645):

    In [22]: from collections import deque
    In [23]: df1 = pd.DataFrame([1, 2, 3])
    In [24]: df2 = pd.DataFrame([4, 5, 6])

    previous behavior:

    In [7]: pd.concat(deque((df1, df2)))
    TypeError: first argument must be a list-like of pandas objects, you passed an object of type "deque"

    current behavior:

    In [25]: pd.concat(deque((df1, df2)))
    0  1
    1  2
    2  3
    0  4
    1  5
    2  6
  • Represent MultiIndex labels with a dtype that utilizes memory based on the level size. In prior versions, the memory usage was a constant 8 bytes per element in each level. In addition, in prior versions, the reported memory usage was incorrect as it didn’t show the usage for the memory occupied by the underling data array. (GH8456)

    In [26]: dfi = DataFrame(1,index=pd.MultiIndex.from_product([['a'],range(1000)]),columns=['A'])

    previous behavior:

    # this was underreported in prior versions
    In [1]: dfi.memory_usage(index=True)
    Index    8000 # took about 24008 bytes in < 0.15.1
    A        8000
    dtype: int64

    current behavior:

    In [27]: dfi.memory_usage(index=True)
    Index    4000
    A        8000
    dtype: int64
  • Added Index properties is_monotonic_increasing and is_monotonic_decreasing (GH8680).

  • Added option to select columns when importing Stata files (GH7935)

  • Qualify memory usage in by adding + if it is a lower bound (GH8578)

  • Raise errors in certain aggregation cases where an argument such as numeric_only is not handled (GH8592).

  • Added support for 3-character ISO and non-standard country codes in (GH8482)

  • World Bank data requests now will warn/raise based on an errors argument, as well as a list of hard-coded country codes and the World Bank’s JSON response. In prior versions, the error messages didn’t look at the World Bank’s JSON response. Problem-inducing input were simply dropped prior to the request. The issue was that many good countries were cropped in the hard-coded approach. All countries will work now, but some bad countries will raise exceptions because some edge cases break the entire response. (GH8482)

  • Added option to Series.str.split() to return a DataFrame rather than a Series (GH8428)

  • Added option to|True|False) to override the default display options and force showing of the null-counts (GH8701)

Bug Fixes

  • Bug in unpickling of a CustomBusinessDay object (GH8591)
  • Bug in coercing Categorical to a records array, e.g. df.to_records() (GH8626)
  • Bug in Categorical not created properly with Series.to_frame() (GH8626)
  • Bug in coercing in astype of a Categorical of a passed pd.Categorical (this now raises TypeError correctly), (GH8626)
  • Bug in cut/qcut when using Series and retbins=True (GH8589)
  • Bug in writing Categorical columns to an SQL database with to_sql (GH8624).
  • Bug in comparing Categorical of datetime raising when being compared to a scalar datetime (GH8687)
  • Bug in selecting from a Categorical with .iloc (GH8623)
  • Bug in groupby-transform with a Categorical (GH8623)
  • Bug in duplicated/drop_duplicates with a Categorical (GH8623)
  • Bug in Categorical reflected comparison operator raising if the first argument was a numpy array scalar (e.g. np.int64) (GH8658)
  • Bug in Panel indexing with a list-like (GH8710)
  • Compat issue is DataFrame.dtypes when options.mode.use_inf_as_null is True (GH8722)
  • Bug in read_csv, dialect parameter would not take a string (:issue: 8703)
  • Bug in slicing a multi-index level with an empty-list (GH8737)
  • Bug in numeric index operations of add/sub with Float/Index Index with numpy arrays (GH8608)
  • Bug in setitem with empty indexer and unwanted coercion of dtypes (GH8669)
  • Bug in ix/loc block splitting on setitem (manifests with integer-like dtypes, e.g. datetime64) (GH8607)
  • Bug when doing label based indexing with integers not found in the index for non-unique but monotonic indexes (GH8680).
  • Bug when indexing a Float64Index with np.nan on numpy 1.7 (GH8980).
  • Fix shape attribute for MultiIndex (GH8609)
  • Bug in GroupBy where a name conflict between the grouper and columns would break groupby operations (GH7115, GH8112)
  • Fixed a bug where plotting a column y and specifying a label would mutate the index name of the original DataFrame (GH8494)
  • Fix regression in plotting of a DatetimeIndex directly with matplotlib (GH8614).
  • Bug in date_range where partially-specified dates would incorporate current date (GH6961)
  • Bug in Setting by indexer to a scalar value with a mixed-dtype Panel4d was failing (GH8702)
  • Bug where DataReader‘s would fail if one of the symbols passed was invalid. Now returns data for valid symbols and np.nan for invalid (GH8494)
  • Bug in get_quote_yahoo that wouldn’t allow non-float return values (GH5229).

v0.15.0 (October 18, 2014)

This is a major release from 0.14.1 and includes a small number of API changes, several new features, enhancements, and performance improvements along with a large number of bug fixes. We recommend that all users upgrade to this version.


pandas >= 0.15.0 will no longer support compatibility with NumPy versions < 1.7.0. If you want to use the latest versions of pandas, please upgrade to NumPy >= 1.7.0 (GH7711)


In 0.15.0 Index has internally been refactored to no longer sub-class ndarray but instead subclass PandasObject, similarly to the rest of the pandas objects. This change allows very easy sub-classing and creation of new index types. This should be a transparent change with only very limited API implications (See the Internal Refactoring)


The refactorings in Categorical changed the two argument constructor from “codes/labels and levels” to “values and levels (now called ‘categories’)”. This can lead to subtle bugs. If you use Categorical directly, please audit your code before updating to this pandas version and change it to use the from_codes() constructor. See more on Categorical here

New features

Categoricals in Series/DataFrame

Categorical can now be included in Series and DataFrames and gained new methods to manipulate. Thanks to Jan Schulz for much of this API/implementation. (GH3943, GH5313, GH5314, GH7444, GH7839, GH7848, GH7864, GH7914, GH7768, GH8006, GH3678, GH8075, GH8076, GH8143, GH8453, GH8518).

For full docs, see the categorical introduction and the API documentation.

In [1]: df = DataFrame({"id":[1,2,3,4,5,6], "raw_grade":['a', 'b', 'b', 'a', 'a', 'e']})

In [2]: df["grade"] = df["raw_grade"].astype("category")

In [3]: df["grade"]
0    a
1    b
2    b
3    a
4    a
5    e
Name: grade, dtype: category
Categories (3, object): [a, b, e]

# Rename the categories
In [4]: df["grade"].cat.categories = ["very good", "good", "very bad"]

# Reorder the categories and simultaneously add the missing categories
In [5]: df["grade"] = df["grade"].cat.set_categories(["very bad", "bad", "medium", "good", "very good"])

In [6]: df["grade"]
0    very good
1         good
2         good
3    very good
4    very good
5     very bad
Name: grade, dtype: category
Categories (5, object): [very bad, bad, medium, good, very good]

In [7]: df.sort("grade")
   id raw_grade      grade
5   6         e   very bad
1   2         b       good
2   3         b       good
0   1         a  very good
3   4         a  very good
4   5         a  very good

In [8]: df.groupby("grade").size()
very bad     1
bad          0
medium       0
good         2
very good    3
dtype: int64
  • pandas.core.group_agg and pandas.core.factor_agg were removed. As an alternative, construct a dataframe and use df.groupby(<group>).agg(<func>).
  • Supplying “codes/labels and levels” to the Categorical constructor is not supported anymore. Supplying two arguments to the constructor is now interpreted as “values and levels (now called ‘categories’)”. Please change your code to use the from_codes() constructor.
  • The Categorical.labels attribute was renamed to and is read only. If you want to manipulate codes, please use one of the API methods on Categoricals.
  • The Categorical.levels attribute is renamed to Categorical.categories.


We introduce a new scalar type Timedelta, which is a subclass of datetime.timedelta, and behaves in a similar manner, but allows compatibility with np.timedelta64 types as well as a host of custom representation, parsing, and attributes. This type is very similar to how Timestamp works for datetimes. It is a nice-API box for the type. See the docs. (GH3009, GH4533, GH8209, GH8187, GH8190, GH7869, GH7661, GH8345, GH8471)


Timedelta scalars (and TimedeltaIndex) component fields are not the same as the component fields on a datetime.timedelta object. For example, .seconds on a datetime.timedelta object returns the total number of seconds combined between hours, minutes and seconds. In contrast, the pandas Timedelta breaks out hours, minutes, microseconds and nanoseconds separately.

# Timedelta accessor
In [9]: tds = Timedelta('31 days 5 min 3 sec')

In [10]: tds.minutes
Out[10]: 5L

In [11]: tds.seconds
Out[11]: 3L

# datetime.timedelta accessor
# this is 5 minutes * 60 + 3 seconds
In [12]: tds.to_pytimedelta().seconds
Out[12]: 303

Note: this is no longer true starting from v0.16.0, where full compatibility with datetime.timedelta is introduced. See the 0.16.0 whatsnew entry


Prior to 0.15.0 pd.to_timedelta would return a Series for list-like/Series input, and a np.timedelta64 for scalar input. It will now return a TimedeltaIndex for list-like input, Series for Series input, and Timedelta for scalar input.

The arguments to pd.to_timedelta are now (arg,unit='ns',box=True,coerce=False), previously were (arg,box=True,unit='ns') as these are more logical.

Consruct a scalar

In [9]: Timedelta('1 days 06:05:01.00003')
Out[9]: Timedelta('1 days 06:05:01.000030')

In [10]: Timedelta('15.5us')
Out[10]: Timedelta('0 days 00:00:00.000015')

In [11]: Timedelta('1 hour 15.5us')
Out[11]: Timedelta('0 days 01:00:00.000015')

# negative Timedeltas have this string repr
# to be more consistent with datetime.timedelta conventions
In [12]: Timedelta('-1us')
Out[12]: Timedelta('-1 days +23:59:59.999999')

# a NaT
In [13]: Timedelta('nan')
Out[13]: NaT

Access fields for a Timedelta

In [14]: td = Timedelta('1 hour 3m 15.5us')

In [15]: td.seconds
Out[15]: 3780L

In [16]: td.microseconds
Out[16]: 15L

In [17]: td.nanoseconds
Out[17]: 500L

Construct a TimedeltaIndex

In [18]: TimedeltaIndex(['1 days','1 days, 00:00:05',
   ....:                 np.timedelta64(2,'D'),timedelta(days=2,seconds=2)])
TimedeltaIndex(['1 days 00:00:00', '1 days 00:00:05', '2 days 00:00:00',
                '2 days 00:00:02'],
               dtype='timedelta64[ns]', freq=None)

Constructing a TimedeltaIndex with a regular range

In [19]: timedelta_range('1 days',periods=5,freq='D')
Out[19]: TimedeltaIndex(['1 days', '2 days', '3 days', '4 days', '5 days'], dtype='timedelta64[ns]', freq='D')

In [20]: timedelta_range(start='1 days',end='2 days',freq='30T')
TimedeltaIndex(['1 days 00:00:00', '1 days 00:30:00', '1 days 01:00:00',
                '1 days 01:30:00', '1 days 02:00:00', '1 days 02:30:00',
                '1 days 03:00:00', '1 days 03:30:00', '1 days 04:00:00',
                '1 days 04:30:00', '1 days 05:00:00', '1 days 05:30:00',
                '1 days 06:00:00', '1 days 06:30:00', '1 days 07:00:00',
                '1 days 07:30:00', '1 days 08:00:00', '1 days 08:30:00',
                '1 days 09:00:00', '1 days 09:30:00', '1 days 10:00:00',
                '1 days 10:30:00', '1 days 11:00:00', '1 days 11:30:00',
                '1 days 12:00:00', '1 days 12:30:00', '1 days 13:00:00',
                '1 days 13:30:00', '1 days 14:00:00', '1 days 14:30:00',
                '1 days 15:00:00', '1 days 15:30:00', '1 days 16:00:00',
                '1 days 16:30:00', '1 days 17:00:00', '1 days 17:30:00',
                '1 days 18:00:00', '1 days 18:30:00', '1 days 19:00:00',
                '1 days 19:30:00', '1 days 20:00:00', '1 days 20:30:00',
                '1 days 21:00:00', '1 days 21:30:00', '1 days 22:00:00',
                '1 days 22:30:00', '1 days 23:00:00', '1 days 23:30:00',
                '2 days 00:00:00'],
               dtype='timedelta64[ns]', freq='30T')

You can now use a TimedeltaIndex as the index of a pandas object

In [21]: s = Series(np.arange(5),
   ....:            index=timedelta_range('1 days',periods=5,freq='s'))

In [22]: s
1 days 00:00:00    0
1 days 00:00:01    1
1 days 00:00:02    2
1 days 00:00:03    3
1 days 00:00:04    4
Freq: S, dtype: int32

You can select with partial string selections

In [23]: s['1 day 00:00:02']
Out[23]: 2

In [24]: s['1 day':'1 day 00:00:02']
1 days 00:00:00    0
1 days 00:00:01    1
1 days 00:00:02    2
Freq: S, dtype: int32

Finally, the combination of TimedeltaIndex with DatetimeIndex allow certain combination operations that are NaT preserving:

In [25]: tdi = TimedeltaIndex(['1 days',pd.NaT,'2 days'])

In [26]: tdi.tolist()
Out[26]: [Timedelta('1 days 00:00:00'), NaT, Timedelta('2 days 00:00:00')]

In [27]: dti = date_range('20130101',periods=3)

In [28]: dti.tolist()
[Timestamp('2013-01-01 00:00:00', offset='D'),
 Timestamp('2013-01-02 00:00:00', offset='D'),
 Timestamp('2013-01-03 00:00:00', offset='D')]

In [29]: (dti + tdi).tolist()
Out[29]: [Timestamp('2013-01-02 00:00:00'), NaT, Timestamp('2013-01-05 00:00:00')]

In [30]: (dti - tdi).tolist()
Out[30]: [Timestamp('2012-12-31 00:00:00'), NaT, Timestamp('2013-01-01 00:00:00')]
  • iteration of a Series e.g. list(Series(...)) of timedelta64[ns] would prior to v0.15.0 return np.timedelta64 for each element. These will now be wrapped in Timedelta.

Memory Usage

Implemented methods to find memory usage of a DataFrame. See the FAQ for more. (GH6852).

A new display option display.memory_usage (see Options and Settings) sets the default behavior of the memory_usage argument in the method. By default display.memory_usage is True.

In [31]: dtypes = ['int64', 'float64', 'datetime64[ns]', 'timedelta64[ns]',
   ....:           'complex128', 'object', 'bool']

In [32]: n = 5000

In [33]: data = dict([ (t, np.random.randint(100, size=n).astype(t))
   ....:                 for t in dtypes])

In [34]: df = DataFrame(data)

In [35]: df['categorical'] = df['object'].astype('category')

In [36]:
<class 'pandas.core.frame.DataFrame'>
Int64Index: 5000 entries, 0 to 4999
Data columns (total 8 columns):
bool               5000 non-null bool
complex128         5000 non-null complex128
datetime64[ns]     5000 non-null datetime64[ns]
float64            5000 non-null float64
int64              5000 non-null int64
object             5000 non-null object
timedelta64[ns]    5000 non-null timedelta64[ns]
categorical        5000 non-null category
dtypes: bool(1), category(1), complex128(1), datetime64[ns](1), float64(1), int64(1), object(1), timedelta64[ns](1)
memory usage: 303.5+ KB

Additionally memory_usage() is an available method for a dataframe object which returns the memory usage of each column.

In [37]: df.memory_usage(index=True)
Index              40000
bool                5000
complex128         80000
datetime64[ns]     40000
float64            40000
int64              40000
object             20000
timedelta64[ns]    40000
categorical         5800
dtype: int64

.dt accessor

Series has gained an accessor to succinctly return datetime like properties for the values of the Series, if its a datetime/period like Series. (GH7207) This will return a Series, indexed like the existing Series. See the docs

# datetime
In [38]: s = Series(date_range('20130101 09:10:12',periods=4))

In [39]: s
0   2013-01-01 09:10:12
1   2013-01-02 09:10:12
2   2013-01-03 09:10:12
3   2013-01-04 09:10:12
dtype: datetime64[ns]

In [40]: s.dt.hour
0    9
1    9
2    9
3    9
dtype: int64

In [41]: s.dt.second
0    12
1    12
2    12
3    12
dtype: int64

In [42]:
0    1
1    2
2    3
3    4
dtype: int64

In [43]: s.dt.freq
Out[43]: <Day>

This enables nice expressions like this:

In [44]: s[]
1   2013-01-02 09:10:12
dtype: datetime64[ns]

You can easily produce tz aware transformations:

In [45]: stz = s.dt.tz_localize('US/Eastern')

In [46]: stz
0   2013-01-01 09:10:12-05:00
1   2013-01-02 09:10:12-05:00
2   2013-01-03 09:10:12-05:00
3   2013-01-04 09:10:12-05:00
dtype: datetime64[ns, US/Eastern]

In [47]:
Out[47]: <DstTzInfo 'US/Eastern' LMT-1 day, 19:04:00 STD>

You can also chain these types of operations:

In [48]: s.dt.tz_localize('UTC').dt.tz_convert('US/Eastern')
0   2013-01-01 04:10:12-05:00
1   2013-01-02 04:10:12-05:00
2   2013-01-03 04:10:12-05:00
3   2013-01-04 04:10:12-05:00
dtype: datetime64[ns, US/Eastern]

The .dt accessor works for period and timedelta dtypes.

# period
In [49]: s = Series(period_range('20130101',periods=4,freq='D'))

In [50]: s
0   2013-01-01
1   2013-01-02
2   2013-01-03
3   2013-01-04
dtype: object

In [51]: s.dt.year
0    2013
1    2013
2    2013
3    2013
dtype: int64

In [52]:
0    1
1    2
2    3
3    4
dtype: int64
# timedelta
In [53]: s = Series(timedelta_range('1 day 00:00:05',periods=4,freq='s'))

In [54]: s
0   1 days 00:00:05
1   1 days 00:00:06
2   1 days 00:00:07
3   1 days 00:00:08
dtype: timedelta64[ns]

In [55]: s.dt.days
0    1
1    1
2    1
3    1
dtype: int64

In [56]: s.dt.seconds
0    5
1    6
2    7
3    8
dtype: int64

In [57]: s.dt.components
   days  hours  minutes  seconds  milliseconds  microseconds  nanoseconds
0     1      0        0        5             0             0            0
1     1      0        0        6             0             0            0
2     1      0        0        7             0             0            0
3     1      0        0        8             0             0            0

Timezone handling improvements

  • tz_localize(None) for tz-aware Timestamp and DatetimeIndex now removes timezone holding local time, previously this resulted in Exception or TypeError (GH7812)

    In [58]: ts = Timestamp('2014-08-01 09:00', tz='US/Eastern')
    In [59]: ts
    Out[59]: Timestamp('2014-08-01 09:00:00-0400', tz='US/Eastern')
    In [60]: ts.tz_localize(None)
    Out[60]: Timestamp('2014-08-01 09:00:00')
    In [61]: didx = DatetimeIndex(start='2014-08-01 09:00', freq='H', periods=10, tz='US/Eastern')
    In [62]: didx
    DatetimeIndex(['2014-08-01 09:00:00-04:00', '2014-08-01 10:00:00-04:00',
                   '2014-08-01 11:00:00-04:00', '2014-08-01 12:00:00-04:00',
                   '2014-08-01 13:00:00-04:00', '2014-08-01 14:00:00-04:00',
                   '2014-08-01 15:00:00-04:00', '2014-08-01 16:00:00-04:00',
                   '2014-08-01 17:00:00-04:00', '2014-08-01 18:00:00-04:00'],
                  dtype='datetime64[ns, US/Eastern]', freq='H')
    In [63]: didx.tz_localize(None)
    DatetimeIndex(['2014-08-01 09:00:00', '2014-08-01 10:00:00',
                   '2014-08-01 11:00:00', '2014-08-01 12:00:00',
                   '2014-08-01 13:00:00', '2014-08-01 14:00:00',
                   '2014-08-01 15:00:00', '2014-08-01 16:00:00',
                   '2014-08-01 17:00:00', '2014-08-01 18:00:00'],
                  dtype='datetime64[ns]', freq='H')
  • tz_localize now accepts the ambiguous keyword which allows for passing an array of bools indicating whether the date belongs in DST or not, ‘NaT’ for setting transition times to NaT, ‘infer’ for inferring DST/non-DST, and ‘raise’ (default) for an AmbiguousTimeError to be raised. See the docs for more details (GH7943)

  • DataFrame.tz_localize and DataFrame.tz_convert now accepts an optional level argument for localizing a specific level of a MultiIndex (GH7846)

  • Timestamp.tz_localize and Timestamp.tz_convert now raise TypeError in error cases, rather than Exception (GH8025)

  • a timeseries/index localized to UTC when inserted into a Series/DataFrame will preserve the UTC timezone (rather than being a naive datetime64[ns]) as object dtype (GH8411)

  • Timestamp.__repr__ displays info (GH7907)

Rolling/Expanding Moments improvements

  • rolling_min(), rolling_max(), rolling_cov(), and rolling_corr() now return objects with all NaN when len(arg) < min_periods <= window rather than raising. (This makes all rolling functions consistent in this behavior). (GH7766)

    Prior to 0.15.0

    In [64]: s = Series([10, 11, 12, 13])
    In [15]: rolling_min(s, window=10, min_periods=5)
    ValueError: min_periods (5) must be <= window (4)

    New behavior

    In [65]: rolling_min(s, window=10, min_periods=5)
    0   NaN
    1   NaN
    2   NaN
    3   NaN
    dtype: float64
  • rolling_max(), rolling_min(), rolling_sum(), rolling_mean(), rolling_median(), rolling_std(), rolling_var(), rolling_skew(), rolling_kurt(), rolling_quantile(), rolling_cov(), rolling_corr(), rolling_corr_pairwise(), rolling_window(), and rolling_apply() with center=True previously would return a result of the same structure as the input arg with NaN in the final (window-1)/2 entries.

    Now the final (window-1)/2 entries of the result are calculated as if the input arg were followed by (window-1)/2 NaN values (or with shrinking windows, in the case of rolling_apply()). (GH7925, GH8269)

    Prior behavior (note final value is NaN):

    In [7]: rolling_sum(Series(range(4)), window=3, min_periods=0, center=True)
    0     1
    1     3
    2     6
    3   NaN
    dtype: float64

    New behavior (note final value is 5 = sum([2, 3, NaN])):

    In [66]: rolling_sum(Series(range(4)), window=3, min_periods=0, center=True)
    0    1
    1    3
    2    6
    3    5
    dtype: float64
  • rolling_window() now normalizes the weights properly in rolling mean mode (mean=True) so that the calculated weighted means (e.g. ‘triang’, ‘gaussian’) are distributed about the same means as those calculated without weighting (i.e. ‘boxcar’). See the note on normalization for further details. (GH7618)

    In [67]: s = Series([10.5, 8.8, 11.4, 9.7, 9.3])

    Behavior prior to 0.15.0:

    In [39]: rolling_window(s, window=3, win_type='triang', center=True)
    0         NaN
    1    6.583333
    2    6.883333
    3    6.683333
    4         NaN
    dtype: float64

    New behavior

    In [68]: rolling_window(s, window=3, win_type='triang', center=True)
    0       NaN
    1     9.875
    2    10.325
    3    10.025
    4       NaN
    dtype: float64
  • Removed center argument from all expanding_ functions (see list), as the results produced when center=True did not make much sense. (GH7925)

  • Added optional ddof argument to expanding_cov() and rolling_cov(). The default value of 1 is backwards-compatible. (GH8279)

  • Documented the ddof argument to expanding_var(), expanding_std(), rolling_var(), and rolling_std(). These functions’ support of a ddof argument (with a default value of 1) was previously undocumented. (GH8064)

  • ewma(), ewmstd(), ewmvol(), ewmvar(), ewmcov(), and ewmcorr() now interpret min_periods in the same manner that the rolling_*() and expanding_*() functions do: a given result entry will be NaN if the (expanding, in this case) window does not contain at least min_periods values. The previous behavior was to set to NaN the min_periods entries starting with the first non- NaN value. (GH7977)

    Prior behavior (note values start at index 2, which is min_periods after index 0 (the index of the first non-empty value)):

    In [69]: s  = Series([1, None, None, None, 2, 3])
    In [51]: ewma(s, com=3., min_periods=2)
    0         NaN
    1         NaN
    2    1.000000
    3    1.000000
    4    1.571429
    5    2.189189
    dtype: float64

    New behavior (note values start at index 4, the location of the 2nd (since min_periods=2) non-empty value):

    In [70]: ewma(s, com=3., min_periods=2)
    0         NaN
    1         NaN
    2         NaN
    3         NaN
    4    1.759644
    5    2.383784
    dtype: float64
  • ewmstd(), ewmvol(), ewmvar(), ewmcov(), and ewmcorr() now have an optional adjust argument, just like ewma() does, affecting how the weights are calculated. The default value of adjust is True, which is backwards-compatible. See Exponentially weighted moment functions for details. (GH7911)

  • ewma(), ewmstd(), ewmvol(), ewmvar(), ewmcov(), and ewmcorr() now have an optional ignore_na argument. When ignore_na=False (the default), missing values are taken into account in the weights calculation. When ignore_na=True (which reproduces the pre-0.15.0 behavior), missing values are ignored in the weights calculation. (GH7543)

    In [71]: ewma(Series([None, 1., 8.]), com=2.)
    0    NaN
    1    1.0
    2    5.2
    dtype: float64
    In [72]: ewma(Series([1., None, 8.]), com=2., ignore_na=True)  # pre-0.15.0 behavior
    0    1.0
    1    1.0
    2    5.2
    dtype: float64
    In [73]: ewma(Series([1., None, 8.]), com=2., ignore_na=False)  # new default
    0    1.000000
    1    1.000000
    2    5.846154
    dtype: float64


    By default (ignore_na=False) the ewm*() functions’ weights calculation in the presence of missing values is different than in pre-0.15.0 versions. To reproduce the pre-0.15.0 calculation of weights in the presence of missing values one must specify explicitly ignore_na=True.

  • Bug in expanding_cov(), expanding_corr(), rolling_cov(), rolling_cor(), ewmcov(), and ewmcorr() returning results with columns sorted by name and producing an error for non-unique columns; now handles non-unique columns and returns columns in original order (except for the case of two DataFrames with pairwise=False, where behavior is unchanged) (GH7542)

  • Bug in rolling_count() and expanding_*() functions unnecessarily producing error message for zero-length data (GH8056)

  • Bug in rolling_apply() and expanding_apply() interpreting min_periods=0 as min_periods=1 (GH8080)

  • Bug in expanding_std() and expanding_var() for a single value producing a confusing error message (GH7900)

  • Bug in rolling_std() and rolling_var() for a single value producing 0 rather than NaN (GH7900)

  • Bug in ewmstd(), ewmvol(), ewmvar(), and ewmcov() calculation of de-biasing factors when bias=False (the default). Previously an incorrect constant factor was used, based on adjust=True, ignore_na=True, and an infinite number of observations. Now a different factor is used for each entry, based on the actual weights (analogous to the usual N/(N-1) factor). In particular, for a single point a value of NaN is returned when bias=False, whereas previously a value of (approximately) 0 was returned.

    For example, consider the following pre-0.15.0 results for ewmvar(..., bias=False), and the corresponding debiasing factors:

    In [74]: s = Series([1., 2., 0., 4.])
    In [89]: ewmvar(s, com=2., bias=False)
    0   -2.775558e-16
    1    3.000000e-01
    2    9.556787e-01
    3    3.585799e+00
    dtype: float64
    In [90]: ewmvar(s, com=2., bias=False) / ewmvar(s, com=2., bias=True)
    0    1.25
    1    1.25
    2    1.25
    3    1.25
    dtype: float64

    Note that entry 0 is approximately 0, and the debiasing factors are a constant 1.25. By comparison, the following 0.15.0 results have a NaN for entry 0, and the debiasing factors are decreasing (towards 1.25):

    In [75]: ewmvar(s, com=2., bias=False)
    0         NaN
    1    0.500000
    2    1.210526
    3    4.089069
    dtype: float64
    In [76]: ewmvar(s, com=2., bias=False) / ewmvar(s, com=2., bias=True)
    0         NaN
    1    2.083333
    2    1.583333
    3    1.425439
    dtype: float64

    See Exponentially weighted moment functions for details. (GH7912)

Improvements in the sql io module

  • Added support for a chunksize parameter to to_sql function. This allows DataFrame to be written in chunks and avoid packet-size overflow errors (GH8062).

  • Added support for a chunksize parameter to read_sql function. Specifying this argument will return an iterator through chunks of the query result (GH2908).

  • Added support for writing and datetime.time object columns with to_sql (GH6932).

  • Added support for specifying a schema to read from/write to with read_sql_table and to_sql (GH7441, GH7952). For example:

    df.to_sql('table', engine, schema='other_schema')
    pd.read_sql_table('table', engine, schema='other_schema')
  • Added support for writing NaN values with to_sql (GH2754).

  • Added support for writing datetime64 columns with to_sql for all database flavors (GH7103).

Backwards incompatible API changes

Breaking changes

API changes related to Categorical (see here for more details):

  • The Categorical constructor with two arguments changed from “codes/labels and levels” to “values and levels (now called ‘categories’)”. This can lead to subtle bugs. If you use Categorical directly, please audit your code by changing it to use the from_codes() constructor.

    An old function call like (prior to 0.15.0):

    pd.Categorical([0,1,0,2,1], levels=['a', 'b', 'c'])

    will have to adapted to the following to keep the same behaviour:

    In [2]: pd.Categorical.from_codes([0,1,0,2,1], categories=['a', 'b', 'c'])
    [a, b, a, c, b]
    Categories (3, object): [a, b, c]

API changes related to the introduction of the Timedelta scalar (see above for more details):

  • Prior to 0.15.0 to_timedelta() would return a Series for list-like/Series input, and a np.timedelta64 for scalar input. It will now return a TimedeltaIndex for list-like input, Series for Series input, and Timedelta for scalar input.

For API changes related to the rolling and expanding functions, see detailed overview above.

Other notable API changes:

  • Consistency when indexing with .loc and a list-like indexer when no values are found.

    In [77]: df = DataFrame([['a'],['b']],index=[1,2])
    In [78]: df
    1  a
    2  b

    In prior versions there was a difference in these two constructs:

    • df.loc[[3]] would return a frame reindexed by 3 (with all np.nan values)
    • df.loc[[3],:] would raise KeyError.

    Both will now raise a KeyError. The rule is that at least 1 indexer must be found when using a list-like and .loc (GH7999)

    Furthermore in prior versions these were also different:

    • df.loc[[1,3]] would return a frame reindexed by [1,3]
    • df.loc[[1,3],:] would raise KeyError.

    Both will now return a frame reindex by [1,3]. E.g.

    In [79]: df.loc[[1,3]]
    1    a
    3  NaN
    In [80]: df.loc[[1,3],:]
    1    a
    3  NaN

    This can also be seen in multi-axis indexing with a Panel.

    In [81]: p = Panel(np.arange(2*3*4).reshape(2,3,4),
       ....:           items=['ItemA','ItemB'],
       ....:           major_axis=[1,2,3],
       ....:           minor_axis=['A','B','C','D'])
    In [82]: p
    <class 'pandas.core.panel.Panel'>
    Dimensions: 2 (items) x 3 (major_axis) x 4 (minor_axis)
    Items axis: ItemA to ItemB
    Major_axis axis: 1 to 3
    Minor_axis axis: A to D

    The following would raise KeyError prior to 0.15.0:

    In [83]: p.loc[['ItemA','ItemD'],:,'D']
       ItemA  ItemD
    1      3    NaN
    2      7    NaN
    3     11    NaN

    Furthermore, .loc will raise If no values are found in a multi-index with a list-like indexer:

    In [84]: s = Series(np.arange(3,dtype='int64'),
       ....:            index=MultiIndex.from_product([['A'],['foo','bar','baz']],
       ....:                                          names=['one','two'])
       ....:           ).sortlevel()
    In [85]: s
    one  two
    A    bar    1
         baz    2
         foo    0
    dtype: int64
    In [86]: try:
       ....:    s.loc[['D']]
       ....: except KeyError as e:
       ....:    print("KeyError: " + str(e))
    KeyError: 'cannot index a multi-index axis with these keys'
  • Assigning values to None now considers the dtype when choosing an ‘empty’ value (GH7941).

    Previously, assigning to None in numeric containers changed the dtype to object (or errored, depending on the call). It now uses NaN:

    In [87]: s = Series([1, 2, 3])
    In [88]: s.loc[0] = None
    In [89]: s
    0   NaN
    1     2
    2     3
    dtype: float64

    NaT is now used similarly for datetime containers.

    For object containers, we now preserve None values (previously these were converted to NaN values).

    In [90]: s = Series(["a", "b", "c"])
    In [91]: s.loc[0] = None
    In [92]: s
    0    None
    1       b
    2       c
    dtype: object

    To insert a NaN, you must explicitly use np.nan. See the docs.

  • In prior versions, updating a pandas object inplace would not reflect in other python references to this object. (GH8511, GH5104)

    In [93]: s = Series([1, 2, 3])
    In [94]: s2 = s
    In [95]: s += 1.5

    Behavior prior to v0.15.0

    # the original object
    In [5]: s
    0    2.5
    1    3.5
    2    4.5
    dtype: float64
    # a reference to the original object
    In [7]: s2
    0    1
    1    2
    2    3
    dtype: int64

    This is now the correct behavior

    # the original object
    In [96]: s
    0    2.5
    1    3.5
    2    4.5
    dtype: float64
    # a reference to the original object
    In [97]: s2
    0    2.5
    1    3.5
    2    4.5
    dtype: float64
  • Made both the C-based and Python engines for read_csv and read_table ignore empty lines in input as well as whitespace-filled lines, as long as sep is not whitespace. This is an API change that can be controlled by the keyword parameter skip_blank_lines. See the docs (GH4466)

  • A timeseries/index localized to UTC when inserted into a Series/DataFrame will preserve the UTC timezone and inserted as object dtype rather than being converted to a naive datetime64[ns] (GH8411).

  • Bug in passing a DatetimeIndex with a timezone that was not being retained in DataFrame construction from a dict (GH7822)

    In prior versions this would drop the timezone, now it retains the timezone, but gives a column of object dtype:

    In [98]: i = date_range('1/1/2011', periods=3, freq='10s', tz = 'US/Eastern')
    In [99]: i
    DatetimeIndex(['2011-01-01 00:00:00-05:00', '2011-01-01 00:00:10-05:00',
                   '2011-01-01 00:00:20-05:00'],
                  dtype='datetime64[ns, US/Eastern]', freq='10S')
    In [100]: df = DataFrame( {'a' : i } )
    In [101]: df
    0 2011-01-01 00:00:00-05:00
    1 2011-01-01 00:00:10-05:00
    2 2011-01-01 00:00:20-05:00
    In [102]: df.dtypes
    a    datetime64[ns, US/Eastern]
    dtype: object

    Previously this would have yielded a column of datetime64 dtype, but without timezone info.

    The behaviour of assigning a column to an existing dataframe as df[‘a’] = i remains unchanged (this already returned an object column with a timezone).

  • When passing multiple levels to stack(), it will now raise a ValueError when the levels aren’t all level names or all level numbers (GH7660). See Reshaping by stacking and unstacking.

  • Raise a ValueError in df.to_hdf with ‘fixed’ format, if df has non-unique columns as the resulting file will be broken (GH7761)

  • SettingWithCopy raise/warnings (according to the option mode.chained_assignment) will now be issued when setting a value on a sliced mixed-dtype DataFrame using chained-assignment. (GH7845, GH7950)

    In [1]: df = DataFrame(np.arange(0,9), columns=['count'])
    In [2]: df['group'] = 'b'
    In [3]: df.iloc[0:5]['group'] = 'a'
    /usr/local/bin/ipython:1: SettingWithCopyWarning:
    A value is trying to be set on a copy of a slice from a DataFrame.
    Try using .loc[row_indexer,col_indexer] = value instead
    See the the caveats in the documentation:
  • merge, DataFrame.merge, and ordered_merge now return the same type as the left argument (GH7737).

  • Previously an enlargement with a mixed-dtype frame would act unlike .append which will preserve dtypes (related GH2578, GH8176):

    In [103]: df = DataFrame([[True, 1],[False, 2]],
       .....:                columns=["female","fitness"])
    In [104]: df
      female  fitness
    0   True        1
    1  False        2
    In [105]: df.dtypes
    female      bool
    fitness    int64
    dtype: object
    # dtypes are now preserved
    In [106]: df.loc[2] = df.loc[1]
    In [107]: df
      female  fitness
    0   True        1
    1  False        2
    2  False        2
    In [108]: df.dtypes
    female      bool
    fitness    int64
    dtype: object
  • Series.to_csv() now returns a string when path=None, matching the behaviour of DataFrame.to_csv() (GH8215).

  • read_hdf now raises IOError when a file that doesn’t exist is passed in. Previously, a new, empty file was created, and a KeyError raised (GH7715).

  • now ends its output with a newline character (GH8114)

  • Concatenating no objects will now raise a ValueError rather than a bare Exception.

  • Merge errors will now be sub-classes of ValueError rather than raw Exception (GH8501)

  • DataFrame.plot and Series.plot keywords are now have consistent orders (GH8037)

Internal Refactoring

In 0.15.0 Index has internally been refactored to no longer sub-class ndarray but instead subclass PandasObject, similarly to the rest of the pandas objects. This change allows very easy sub-classing and creation of new index types. This should be a transparent change with only very limited API implications (GH5080, GH7439, GH7796, GH8024, GH8367, GH7997, GH8522):

  • you may need to unpickle pandas version < 0.15.0 pickles using pd.read_pickle rather than pickle.load. See pickle docs
  • when plotting with a PeriodIndex, the matplotlib internal axes will now be arrays of Period rather than a PeriodIndex (this is similar to how a DatetimeIndex passes arrays of datetimes now)
  • MultiIndexes will now raise similary to other pandas objects w.r.t. truth testing, see here (GH7897).
  • When plotting a DatetimeIndex directly with matplotlib’s plot function, the axis labels will no longer be formatted as dates but as integers (the internal representation of a datetime64). UPDATE This is fixed in 0.15.1, see here.


  • The attributes Categorical labels and levels attributes are deprecated and renamed to codes and categories.
  • The outtype argument to pd.DataFrame.to_dict has been deprecated in favor of orient. (GH7840)
  • The convert_dummies method has been deprecated in favor of get_dummies (GH8140)
  • The infer_dst argument in tz_localize will be deprecated in favor of ambiguous to allow for more flexibility in dealing with DST transitions. Replace infer_dst=True with ambiguous='infer' for the same behavior (GH7943). See the docs for more details.
  • The top-level pd.value_range has been deprecated and can be replaced by .describe() (GH8481)
  • The Index set operations + and - were deprecated in order to provide these for numeric type operations on certain index types. + can be replaced by .union() or |, and - by .difference(). Further the method name Index.diff() is deprecated and can be replaced by Index.difference() (GH8226)

    # +
    Index(['a','b','c']) + Index(['b','c','d'])
    # should be replaced by
    # -
    Index(['a','b','c']) - Index(['b','c','d'])
    # should be replaced by
  • The infer_types argument to read_html() now has no effect and is deprecated (GH7762, GH7032).

Removal of prior version deprecations/changes

  • Remove DataFrame.delevel method in favor of DataFrame.reset_index


Enhancements in the importing/exporting of Stata files:

  • Added support for bool, uint8, uint16 and uint32 datatypes in to_stata (GH7097, GH7365)
  • Added conversion option when importing Stata files (GH8527)
  • DataFrame.to_stata and StataWriter check string length for compatibility with limitations imposed in dta files where fixed-width strings must contain 244 or fewer characters. Attempting to write Stata dta files with strings longer than 244 characters raises a ValueError. (GH7858)
  • read_stata and StataReader can import missing data information into a DataFrame by setting the argument convert_missing to True. When using this options, missing values are returned as StataMissingValue objects and columns containing missing values have object data type. (GH8045)

Enhancements in the plotting functions:

  • Added layout keyword to DataFrame.plot. You can pass a tuple of (rows, columns), one of which can be -1 to automatically infer (GH6667, GH8071).
  • Allow to pass multiple axes to DataFrame.plot, hist and boxplot (GH5353, GH6970, GH7069)
  • Added support for c, colormap and colorbar arguments for DataFrame.plot with kind='scatter' (GH7780)
  • Histogram from DataFrame.plot with kind='hist' (GH7809), See the docs.
  • Boxplot from DataFrame.plot with kind='box' (GH7998), See the docs.


  • read_csv now has a keyword parameter float_precision which specifies which floating-point converter the C engine should use during parsing, see here (GH8002, GH8044)

  • Added searchsorted method to Series objects (GH7447)

  • describe() on mixed-types DataFrames is more flexible. Type-based column filtering is now possible via the include/exclude arguments. See the docs (GH8164).

    In [109]: df = DataFrame({'catA': ['foo', 'foo', 'bar'] * 8,
       .....:                 'catB': ['a', 'b', 'c', 'd'] * 6,
       .....:                 'numC': np.arange(24),
       .....:                 'numD': np.arange(24.) + .5})
    In [110]: df.describe(include=["object"])
           catA catB
    count    24   24
    unique    2    4
    top     foo    d
    freq     16    6
    In [111]: df.describe(include=["number", "object"], exclude=["float"])
           catA catB       numC
    count    24   24  24.000000
    unique    2    4        NaN
    top     foo    d        NaN
    freq     16    6        NaN
    mean    NaN  NaN  11.500000
    std     NaN  NaN   7.071068
    min     NaN  NaN   0.000000
    25%     NaN  NaN   5.750000
    50%     NaN  NaN  11.500000
    75%     NaN  NaN  17.250000
    max     NaN  NaN  23.000000

    Requesting all columns is possible with the shorthand ‘all’

    In [112]: df.describe(include='all')
           catA catB       numC       numD
    count    24   24  24.000000  24.000000
    unique    2    4        NaN        NaN
    top     foo    d        NaN        NaN
    freq     16    6        NaN        NaN
    mean    NaN  NaN  11.500000  12.000000
    std     NaN  NaN   7.071068   7.071068
    min     NaN  NaN   0.000000   0.500000
    25%     NaN  NaN   5.750000   6.250000
    50%     NaN  NaN  11.500000  12.000000
    75%     NaN  NaN  17.250000  17.750000
    max     NaN  NaN  23.000000  23.500000

    Without those arguments, ‘describe` will behave as before, including only numerical columns or, if none are, only categorical columns. See also the docs

  • Added split as an option to the orient argument in pd.DataFrame.to_dict. (GH7840)

  • The get_dummies method can now be used on DataFrames. By default only catagorical columns are encoded as 0’s and 1’s, while other columns are left untouched.

    In [113]: df = DataFrame({'A': ['a', 'b', 'a'], 'B': ['c', 'c', 'b'],
       .....:                 'C': [1, 2, 3]})
    In [114]: pd.get_dummies(df)
       C  A_a  A_b  B_b  B_c
    0  1    1    0    0    1
    1  2    0    1    0    1
    2  3    1    0    1    0
  • PeriodIndex supports resolution as the same as DatetimeIndex (GH7708)

  • has added support for additional holidays and ways to observe holidays (GH7070)

  • now supports a list of offsets in Python3 (GH7070)

  • now supports a days_of_week parameter (GH7070)

  • GroupBy.nth() now supports selecting multiple nth values (GH7910)

    In [115]: business_dates = date_range(start='4/1/2014', end='6/30/2014', freq='B')
    In [116]: df = DataFrame(1, index=business_dates, columns=['a', 'b'])
    # get the first, 4th, and last date index for each month
    In [117]: df.groupby((df.index.year, df.index.month)).nth([0, 3, -1])
                a  b
    2014-04-01  1  1
    2014-04-04  1  1
    2014-04-30  1  1
    2014-05-01  1  1
    2014-05-06  1  1
    2014-05-30  1  1
    2014-06-02  1  1
    2014-06-05  1  1
    2014-06-30  1  1
  • Period and PeriodIndex supports addition/subtraction with timedelta-likes (GH7966)

    If Period freq is D, H, T, S, L, U, N, Timedelta-like can be added if the result can have same freq. Otherwise, only the same offsets can be added.

    In [118]: idx = pd.period_range('2014-07-01 09:00', periods=5, freq='H')
    In [119]: idx
    PeriodIndex(['2014-07-01 09:00', '2014-07-01 10:00', '2014-07-01 11:00',
                 '2014-07-01 12:00', '2014-07-01 13:00'],
                dtype='int64', freq='H')
    In [120]: idx + pd.offsets.Hour(2)
    PeriodIndex(['2014-07-01 11:00', '2014-07-01 12:00', '2014-07-01 13:00',
                 '2014-07-01 14:00', '2014-07-01 15:00'],
                dtype='int64', freq='H')
    In [121]: idx + Timedelta('120m')
    PeriodIndex(['2014-07-01 11:00', '2014-07-01 12:00', '2014-07-01 13:00',
                 '2014-07-01 14:00', '2014-07-01 15:00'],
                dtype='int64', freq='H')
    In [122]: idx = pd.period_range('2014-07', periods=5, freq='M')
    In [123]: idx
    Out[123]: PeriodIndex(['2014-07', '2014-08', '2014-09', '2014-10', '2014-11'], dtype='int64', freq='M')
    In [124]: idx + pd.offsets.MonthEnd(3)
    Out[124]: PeriodIndex(['2014-10', '2014-11', '2014-12', '2015-01', '2015-02'], dtype='int64', freq='M')
  • Added experimental compatibility with openpyxl for versions >= 2.0. The DataFrame.to_excel method engine keyword now recognizes openpyxl1 and openpyxl2 which will explicitly require openpyxl v1 and v2 respectively, failing if the requested version is not available. The openpyxl engine is a now a meta-engine that automatically uses whichever version of openpyxl is installed. (GH7177)

  • DataFrame.fillna can now accept a DataFrame as a fill value (GH8377)

  • Passing multiple levels to stack() will now work when multiple level numbers are passed (GH7660). See Reshaping by stacking and unstacking.

  • set_names(), set_labels(), and set_levels() methods now take an optional level keyword argument to all modification of specific level(s) of a MultiIndex. Additionally set_names() now accepts a scalar string value when operating on an Index or on a specific level of a MultiIndex (GH7792)

    In [125]: idx = MultiIndex.from_product([['a'], range(3), list("pqr")], names=['foo', 'bar', 'baz'])
    In [126]: idx.set_names('qux', level=0)
    MultiIndex(levels=[[u'a'], [0, 1, 2], [u'p', u'q', u'r']],
               labels=[[0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 1, 1, 1, 2, 2, 2], [0, 1, 2, 0, 1, 2, 0, 1, 2]],
               names=[u'qux', u'bar', u'baz'])
    In [127]: idx.set_names(['qux','baz'], level=[0,1])
    MultiIndex(levels=[[u'a'], [0, 1, 2], [u'p', u'q', u'r']],
               labels=[[0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 1, 1, 1, 2, 2, 2], [0, 1, 2, 0, 1, 2, 0, 1, 2]],
               names=[u'qux', u'baz', u'baz'])
    In [128]: idx.set_levels(['a','b','c'], level='bar')
    MultiIndex(levels=[[u'a'], [u'a', u'b', u'c'], [u'p', u'q', u'r']],
               labels=[[0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 1, 1, 1, 2, 2, 2], [0, 1, 2, 0, 1, 2, 0, 1, 2]],
               names=[u'foo', u'bar', u'baz'])
    In [129]: idx.set_levels([['a','b','c'],[1,2,3]], level=[1,2])
    MultiIndex(levels=[[u'a'], [u'a', u'b', u'c'], [1, 2, 3]],
               labels=[[0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 1, 1, 1, 2, 2, 2], [0, 1, 2, 0, 1, 2, 0, 1, 2]],
               names=[u'foo', u'bar', u'baz'])
  • Index.isin now supports a level argument to specify which index level to use for membership tests (GH7892, GH7890)

    In [1]: idx = MultiIndex.from_product([[0, 1], ['a', 'b', 'c']])
    In [2]: idx.values
    Out[2]: array([(0, 'a'), (0, 'b'), (0, 'c'), (1, 'a'), (1, 'b'), (1, 'c')], dtype=object)
    In [3]: idx.isin(['a', 'c', 'e'], level=1)
    Out[3]: array([ True, False,  True,  True, False,  True], dtype=bool)
  • Index now supports duplicated and drop_duplicates. (GH4060)

    In [130]: idx = Index([1, 2, 3, 4, 1, 2])
    In [131]: idx
    Out[131]: Int64Index([1, 2, 3, 4, 1, 2], dtype='int64')
    In [132]: idx.duplicated()
    Out[132]: array([False, False, False, False,  True,  True], dtype=bool)
    In [133]: idx.drop_duplicates()
    Out[133]: Int64Index([1, 2, 3, 4], dtype='int64')
  • add copy=True argument to pd.concat to enable pass thru of complete blocks (GH8252)

  • Added support for numpy 1.8+ data types (bool_, int_, float_, string_) for conversion to R dataframe (GH8400)


  • Performance improvements in DatetimeIndex.__iter__ to allow faster iteration (GH7683)
  • Performance improvements in Period creation (and PeriodIndex setitem) (GH5155)
  • Improvements in Series.transform for significant performance gains (revised) (GH6496)
  • Performance improvements in StataReader when reading large files (GH8040, GH8073)
  • Performance improvements in StataWriter when writing large files (GH8079)
  • Performance and memory usage improvements in multi-key groupby (GH8128)
  • Performance improvements in groupby .agg and .apply where builtins max/min were not mapped to numpy/cythonized versions (GH7722)
  • Performance improvement in writing to sql (to_sql) of up to 50% (GH8208).
  • Performance benchmarking of groupby for large value of ngroups (GH6787)
  • Performance improvement in CustomBusinessDay, CustomBusinessMonth (GH8236)
  • Performance improvement for MultiIndex.values for multi-level indexes containing datetimes (GH8543)

Bug Fixes

  • Bug in pivot_table, when using margins and a dict aggfunc (GH8349)
  • Bug in read_csv where squeeze=True would return a view (GH8217)
  • Bug in checking of table name in read_sql in certain cases (GH7826).
  • Bug in DataFrame.groupby where Grouper does not recognize level when frequency is specified (GH7885)
  • Bug in multiindexes dtypes getting mixed up when DataFrame is saved to SQL table (GH8021)
  • Bug in Series 0-division with a float and integer operand dtypes (GH7785)
  • Bug in Series.astype("unicode") not calling unicode on the values correctly (GH7758)
  • Bug in DataFrame.as_matrix() with mixed datetime64[ns] and timedelta64[ns] dtypes (GH7778)
  • Bug in HDFStore.select_column() not preserving UTC timezone info when selecting a DatetimeIndex (GH7777)
  • Bug in to_datetime when format='%Y%m%d' and coerce=True are specified, where previously an object array was returned (rather than a coerced time-series with NaT), (GH7930)
  • Bug in DatetimeIndex and PeriodIndex in-place addition and subtraction cause different result from normal one (GH6527)
  • Bug in adding and subtracting PeriodIndex with PeriodIndex raise TypeError (GH7741)
  • Bug in combine_first with PeriodIndex data raises TypeError (GH3367)
  • Bug in multi-index slicing with missing indexers (GH7866)
  • Bug in multi-index slicing with various edge cases (GH8132)
  • Regression in multi-index indexing with a non-scalar type object (GH7914)
  • Bug in Timestamp comparisons with == and int64 dtype (GH8058)
  • Bug in pickles contains DateOffset may raise AttributeError when normalize attribute is reffered internally (GH7748)
  • Bug in Panel when using major_xs and copy=False is passed (deprecation warning fails because of missing warnings) (GH8152).
  • Bug in pickle deserialization that failed for pre-0.14.1 containers with dup items trying to avoid ambiguity when matching block and manager items, when there’s only one block there’s no ambiguity (GH7794)
  • Bug in putting a PeriodIndex into a Series would convert to int64 dtype, rather than object of Periods (GH7932)
  • Bug in HDFStore iteration when passing a where (GH8014)
  • Bug in DataFrameGroupby.transform when transforming with a passed non-sorted key (GH8046, GH8430)
  • Bug in repeated timeseries line and area plot may result in ValueError or incorrect kind (GH7733)
  • Bug in inference in a MultiIndex with inputs (GH7888)
  • Bug in get where an IndexError would not cause the default value to be returned (GH7725)
  • Bug in offsets.apply, rollforward and rollback may reset nanosecond (GH7697)
  • Bug in offsets.apply, rollforward and rollback may raise AttributeError if Timestamp has dateutil tzinfo (GH7697)
  • Bug in sorting a multi-index frame with a Float64Index (GH8017)
  • Bug in inconsistent panel setitem with a rhs of a DataFrame for alignment (GH7763)
  • Bug in is_superperiod and is_subperiod cannot handle higher frequencies than S (GH7760, GH7772, GH7803)
  • Bug in 32-bit platforms with Series.shift (GH8129)
  • Bug in PeriodIndex.unique returns int64 np.ndarray (GH7540)
  • Bug in groupby.apply with a non-affecting mutation in the function (GH8467)
  • Bug in DataFrame.reset_index which has MultiIndex contains PeriodIndex or DatetimeIndex with tz raises ValueError (GH7746, GH7793)
  • Bug in DataFrame.plot with subplots=True may draw unnecessary minor xticks and yticks (GH7801)
  • Bug in StataReader which did not read variable labels in 117 files due to difference between Stata documentation and implementation (GH7816)
  • Bug in StataReader where strings were always converted to 244 characters-fixed width irrespective of underlying string size (GH7858)
  • Bug in DataFrame.plot and Series.plot may ignore rot and fontsize keywords (GH7844)
  • Bug in DatetimeIndex.value_counts doesn’t preserve tz (GH7735)
  • Bug in PeriodIndex.value_counts results in Int64Index (GH7735)
  • Bug in DataFrame.join when doing left join on index and there are multiple matches (GH5391)
  • Bug in GroupBy.transform() where int groups with a transform that didn’t preserve the index were incorrectly truncated (GH7972).
  • Bug in groupby where callable objects without name attributes would take the wrong path, and produce a DataFrame instead of a Series (GH7929)
  • Bug in groupby error message when a DataFrame grouping column is duplicated (GH7511)
  • Bug in read_html where the infer_types argument forced coercion of date-likes incorrectly (GH7762, GH7032).
  • Bug in with an index which was filtered as to not include the first item (GH7857)
  • Bug in Timestamp cannot parse nanosecond from string (GH7878)
  • Bug in Timestamp with string offset and tz results incorrect (GH7833)
  • Bug in tslib.tz_convert and tslib.tz_convert_single may return different results (GH7798)
  • Bug in DatetimeIndex.intersection of non-overlapping timestamps with tz raises IndexError (GH7880)
  • Bug in alignment with TimeOps and non-unique indexes (GH8363)
  • Bug in GroupBy.filter() where fast path vs. slow path made the filter return a non scalar value that appeared valid but wasn’t (GH7870).
  • Bug in date_range()/DatetimeIndex() when the timezone was inferred from input dates yet incorrect times were returned when crossing DST boundaries (GH7835, GH7901).
  • Bug in to_excel() where a negative sign was being prepended to positive infinity and was absent for negative infinity (GH7949)
  • Bug in area plot draws legend with incorrect alpha when stacked=True (GH8027)
  • Period and PeriodIndex addition/subtraction with np.timedelta64 results in incorrect internal representations (GH7740)
  • Bug in Holiday with no offset or observance (GH7987)
  • Bug in DataFrame.to_latex formatting when columns or index is a MultiIndex (GH7982).
  • Bug in DateOffset around Daylight Savings Time produces unexpected results (GH5175).
  • Bug in DataFrame.shift where empty columns would throw ZeroDivisionError on numpy 1.7 (GH8019)
  • Bug in installation where html_encoding/*.html wasn’t installed and therefore some tests were not running correctly (GH7927).
  • Bug in read_html where bytes objects were not tested for in _read (GH7927).
  • Bug in DataFrame.stack() when one of the column levels was a datelike (GH8039)
  • Bug in broadcasting numpy scalars with DataFrame (GH8116)
  • Bug in pivot_table performed with nameless index and columns raises KeyError (GH8103)
  • Bug in DataFrame.plot(kind='scatter') draws points and errorbars with different colors when the color is specified by c keyword (GH8081)
  • Bug in Float64Index where iat and at were not testing and were failing (GH8092).
  • Bug in DataFrame.boxplot() where y-limits were not set correctly when producing multiple axes (GH7528, GH5517).
  • Bug in read_csv where line comments were not handled correctly given a custom line terminator or delim_whitespace=True (GH8122).
  • Bug in read_html where empty tables caused a StopIteration (GH7575)
  • Bug in casting when setting a column in a same-dtype block (GH7704)
  • Bug in accessing groups from a GroupBy when the original grouper was a tuple (GH8121).
  • Bug in .at that would accept integer indexers on a non-integer index and do fallback (GH7814)
  • Bug with kde plot and NaNs (GH8182)
  • Bug in GroupBy.count with float32 data type were nan values were not excluded (GH8169).
  • Bug with stacked barplots and NaNs (GH8175).
  • Bug in resample with non evenly divisible offsets (e.g. ‘7s’) (GH8371)
  • Bug in interpolation methods with the limit keyword when no values needed interpolating (GH7173).
  • Bug where col_space was ignored in DataFrame.to_string() when header=False (GH8230).
  • Bug with DatetimeIndex.asof incorrectly matching partial strings and returning the wrong date (GH8245).
  • Bug in plotting methods modifying the global matplotlib rcParams (GH8242).
  • Bug in DataFrame.__setitem__ that caused errors when setting a dataframe column to a sparse array (GH8131)
  • Bug where Dataframe.boxplot() failed when entire column was empty (GH8181).
  • Bug with messed variables in radviz visualization (GH8199).
  • Bug in interpolation methods with the limit keyword when no values needed interpolating (GH7173).
  • Bug where col_space was ignored in DataFrame.to_string() when header=False (GH8230).
  • Bug in to_clipboard that would clip long column data (GH8305)
  • Bug in DataFrame terminal display: Setting max_column/max_rows to zero did not trigger auto-resizing of dfs to fit terminal width/height (GH7180).
  • Bug in OLS where running with “cluster” and “nw_lags” parameters did not work correctly, but also did not throw an error (GH5884).
  • Bug in DataFrame.dropna that interpreted non-existent columns in the subset argument as the ‘last column’ (GH8303)
  • Bug in Index.intersection on non-monotonic non-unique indexes (GH8362).
  • Bug in masked series assignment where mismatching types would break alignment (GH8387)
  • Bug in NDFrame.equals gives false negatives with dtype=object (GH8437)
  • Bug in assignment with indexer where type diversity would break alignment (GH8258)
  • Bug in NDFrame.loc indexing when row/column names were lost when target was a list/ndarray (GH6552)
  • Regression in NDFrame.loc indexing when rows/columns were converted to Float64Index if target was an empty list/ndarray (GH7774)
  • Bug in Series that allows it to be indexed by a DataFrame which has unexpected results. Such indexing is no longer permitted (GH8444)
  • Bug in item assignment of a DataFrame with multi-index columns where right-hand-side columns were not aligned (GH7655)
  • Suppress FutureWarning generated by NumPy when comparing object arrays containing NaN for equality (GH7065)
  • Bug in DataFrame.eval() where the dtype of the not operator (~) was not correctly inferred as bool.

v0.14.1 (July 11, 2014)

This is a minor release from 0.14.0 and includes a small number of API changes, several new features, enhancements, and performance improvements along with a large number of bug fixes. We recommend that all users upgrade to this version.

API changes

  • Openpyxl now raises a ValueError on construction of the openpyxl writer instead of warning on pandas import (GH7284).

  • For StringMethods.extract, when no match is found, the result - only containing NaN values - now also has dtype=object instead of float (GH7242)

  • Period objects no longer raise a TypeError when compared using == with another object that isn’t a Period. Instead when comparing a Period with another object using == if the other object isn’t a Period False is returned. (GH7376)

  • Previously, the behaviour on resetting the time or not in offsets.apply, rollforward and rollback operations differed between offsets. With the support of the normalize keyword for all offsets(see below) with a default value of False (preserve time), the behaviour changed for certain offsets (BusinessMonthBegin, MonthEnd, BusinessMonthEnd, CustomBusinessMonthEnd, BusinessYearBegin, LastWeekOfMonth, FY5253Quarter, LastWeekOfMonth, Easter):

    In [6]: from pandas.tseries import offsets
    In [7]: d = pd.Timestamp('2014-01-01 09:00')
    # old behaviour < 0.14.1
    In [8]: d + offsets.MonthEnd()
    Out[8]: Timestamp('2014-01-31 00:00:00')

    Starting from 0.14.1 all offsets preserve time by default. The old behaviour can be obtained with normalize=True

    # new behaviour
    In [1]: d + offsets.MonthEnd()
    Out[1]: Timestamp('2014-01-31 09:00:00')
    In [2]: d + offsets.MonthEnd(normalize=True)
    Out[2]: Timestamp('2014-01-31 00:00:00')

    Note that for the other offsets the default behaviour did not change.

  • Add back #N/A N/A as a default NA value in text parsing, (regresion from 0.12) (GH5521)

  • Raise a TypeError on inplace-setting with a .where and a non np.nan value as this is inconsistent with a set-item expression like df[mask] = None (GH7656)


  • Add dropna argument to value_counts and nunique (GH5569).

  • Add select_dtypes() method to allow selection of columns based on dtype (GH7316). See the docs.

  • All offsets suppports the normalize keyword to specify whether offsets.apply, rollforward and rollback resets the time (hour, minute, etc) or not (default False, preserves time) (GH7156):

    In [3]: import pandas.tseries.offsets as offsets
    In [4]: day = offsets.Day()
    In [5]: day.apply(Timestamp('2014-01-01 09:00'))
    Out[5]: Timestamp('2014-01-02 09:00:00')
    In [6]: day = offsets.Day(normalize=True)
    In [7]: day.apply(Timestamp('2014-01-01 09:00'))
    Out[7]: Timestamp('2014-01-02 00:00:00')
  • PeriodIndex is represented as the same format as DatetimeIndex (GH7601)

  • StringMethods now work on empty Series (GH7242)

  • The file parsers read_csv and read_table now ignore line comments provided by the parameter comment, which accepts only a single character for the C reader. In particular, they allow for comments before file data begins (GH2685)

  • Add NotImplementedError for simultaneous use of chunksize and nrows for read_csv() (GH6774).

  • Tests for basic reading of public S3 buckets now exist (GH7281).

  • read_html now sports an encoding argument that is passed to the underlying parser library. You can use this to read non-ascii encoded web pages (GH7323).

  • read_excel now supports reading from URLs in the same way that read_csv does. (GH6809)

  • Support for dateutil timezones, which can now be used in the same way as pytz timezones across pandas. (GH4688)

    In [8]: rng = date_range('3/6/2012 00:00', periods=10, freq='D',
       ...:                  tz='dateutil/Europe/London')
    In [9]:
    Out[9]: tzfile('/usr/share/zoneinfo/Europe/London')

    See the docs.

  • Implemented sem (standard error of the mean) operation for Series, DataFrame, Panel, and Groupby (GH6897)

  • Add nlargest and nsmallest to the Series groupby whitelist, which means you can now use these methods on a SeriesGroupBy object (GH7053).

  • All offsets apply, rollforward and rollback can now handle np.datetime64, previously results in ApplyTypeError (GH7452)

  • Period and PeriodIndex can contain NaT in its values (GH7485)

  • Support pickling Series, DataFrame and Panel objects with non-unique labels along item axis (index, columns and items respectively) (GH7370).

  • Improved inference of datetime/timedelta with mixed null objects. Regression from 0.13.1 in interpretation of an object Index with all null elements (GH7431)


  • Improvements in dtype inference for numeric operations involving yielding performance gains for dtypes: int64, timedelta64, datetime64 (GH7223)
  • Improvements in Series.transform for significant performance gains (GH6496)
  • Improvements in DataFrame.transform with ufuncs and built-in grouper functions for signifcant performance gains (GH7383)
  • Regression in groupby aggregation of datetime64 dtypes (GH7555)
  • Improvements in MultiIndex.from_product for large iterables (GH7627)


  • has a new method, get_all_data method, and now consistently returns a multi-indexed DataFrame, see the docs. (GH5602)
  • io.gbq.read_gbq and io.gbq.to_gbq were refactored to remove the dependency on the Google command line client. This submodule now uses httplib2 and the Google apiclient and oauth2client API client libraries which should be more stable and, therefore, reliable than See the docs. (GH6937).

Bug Fixes

  • Bug in DataFrame.where with a symmetric shaped frame and a passed other of a DataFrame (GH7506)
  • Bug in Panel indexing with a multi-index axis (GH7516)
  • Regression in datetimelike slice indexing with a duplicated index and non-exact end-points (GH7523)
  • Bug in setitem with list-of-lists and single vs mixed types (GH7551:)
  • Bug in timeops with non-aligned Series (GH7500)
  • Bug in timedelta inference when assigning an incomplete Series (GH7592)
  • Bug in groupby .nth with a Series and integer-like column name (GH7559)
  • Bug in Series.get with a boolean accessor (GH7407)
  • Bug in value_counts where NaT did not qualify as missing (NaN) (GH7423)
  • Bug in to_timedelta that accepted invalid units and misinterpreted ‘m/h’ (GH7611, GH6423)
  • Bug in line plot doesn’t set correct xlim if secondary_y=True (GH7459)
  • Bug in grouped hist and scatter plots use old figsize default (GH7394)
  • Bug in plotting subplots with DataFrame.plot, hist clears passed ax even if the number of subplots is one (GH7391).
  • Bug in plotting subplots with DataFrame.boxplot with by kw raises ValueError if the number of subplots exceeds 1 (GH7391).
  • Bug in subplots displays ticklabels and labels in different rule (GH5897)
  • Bug in Panel.apply with a multi-index as an axis (GH7469)
  • Bug in DatetimeIndex.insert doesn’t preserve name and tz (GH7299)
  • Bug in DatetimeIndex.asobject doesn’t preserve name (GH7299)
  • Bug in multi-index slicing with datetimelike ranges (strings and Timestamps), (GH7429)
  • Bug in Index.min and max doesn’t handle nan and NaT properly (GH7261)
  • Bug in PeriodIndex.min/max results in int (GH7609)
  • Bug in resample where fill_method was ignored if you passed how (GH2073)
  • Bug in TimeGrouper doesn’t exclude column specified by key (GH7227)
  • Bug in DataFrame and Series bar and barh plot raises TypeError when bottom and left keyword is specified (GH7226)
  • Bug in DataFrame.hist raises TypeError when it contains non numeric column (GH7277)
  • Bug in Index.delete does not preserve name and freq attributes (GH7302)
  • Bug in DataFrame.query()/eval where local string variables with the @ sign were being treated as temporaries attempting to be deleted (GH7300).
  • Bug in Float64Index which didn’t allow duplicates (GH7149).
  • Bug in DataFrame.replace() where truthy values were being replaced (GH7140).
  • Bug in StringMethods.extract() where a single match group Series would use the matcher’s name instead of the group name (GH7313).
  • Bug in isnull() when mode.use_inf_as_null == True where isnull wouldn’t test True when it encountered an inf/-inf (GH7315).
  • Bug in inferred_freq results in None for eastern hemisphere timezones (GH7310)
  • Bug in Easter returns incorrect date when offset is negative (GH7195)
  • Bug in broadcasting with .div, integer dtypes and divide-by-zero (GH7325)
  • Bug in CustomBusinessDay.apply raiases NameError when np.datetime64 object is passed (GH7196)
  • Bug in MultiIndex.append, concat and pivot_table don’t preserve timezone (GH6606)
  • Bug in .loc with a list of indexers on a single-multi index level (that is not nested) (GH7349)
  • Bug in when mapping a dict with tuple keys of different lengths (GH7333)
  • Bug all StringMethods now work on empty Series (GH7242)
  • Fix delegation of read_sql to read_sql_query when query does not contain ‘select’ (GH7324).
  • Bug where a string column name assignment to a DataFrame with a Float64Index raised a TypeError during a call to np.isnan (GH7366).
  • Bug where NDFrame.replace() didn’t correctly replace objects with Period values (GH7379).
  • Bug in .ix getitem should always return a Series (GH7150)
  • Bug in multi-index slicing with incomplete indexers (GH7399)
  • Bug in multi-index slicing with a step in a sliced level (GH7400)
  • Bug where negative indexers in DatetimeIndex were not correctly sliced (GH7408)
  • Bug where NaT wasn’t repr’d correctly in a MultiIndex (GH7406, GH7409).
  • Bug where bool objects were converted to nan in convert_objects (GH7416).
  • Bug in quantile ignoring the axis keyword argument (:issue`7306`)
  • Bug where nanops._maybe_null_out doesn’t work with complex numbers (GH7353)
  • Bug in several nanops functions when axis==0 for 1-dimensional nan arrays (GH7354)
  • Bug where nanops.nanmedian doesn’t work when axis==None (GH7352)
  • Bug where nanops._has_infs doesn’t work with many dtypes (GH7357)
  • Bug in where reading a 0-observation dta failed (GH7369)
  • Bug in StataReader when reading Stata 13 (117) files containing fixed width strings (GH7360)
  • Bug in StataWriter where encoding was ignored (GH7286)
  • Bug in DatetimeIndex comparison doesn’t handle NaT properly (GH7529)
  • Bug in passing input with tzinfo to some offsets apply, rollforward or rollback resets tzinfo or raises ValueError (GH7465)
  • Bug in DatetimeIndex.to_period, PeriodIndex.asobject, PeriodIndex.to_timestamp doesn’t preserve name (GH7485)
  • Bug in DatetimeIndex.to_period and PeriodIndex.to_timestanp handle NaT incorrectly (GH7228)
  • Bug in offsets.apply, rollforward and rollback may return normal datetime (GH7502)
  • Bug in resample raises ValueError when target contains NaT (GH7227)
  • Bug in Timestamp.tz_localize resets nanosecond info (GH7534)
  • Bug in DatetimeIndex.asobject raises ValueError when it contains NaT (GH7539)
  • Bug in Timestamp.__new__ doesn’t preserve nanosecond properly (GH7610)
  • Bug in Index.astype(float) where it would return an object dtype Index (GH7464).
  • Bug in DataFrame.reset_index loses tz (GH3950)
  • Bug in DatetimeIndex.freqstr raises AttributeError when freq is None (GH7606)
  • Bug in GroupBy.size created by TimeGrouper raises AttributeError (GH7453)
  • Bug in single column bar plot is misaligned (GH7498).
  • Bug in area plot with tz-aware time series raises ValueError (GH7471)
  • Bug in non-monotonic Index.union may preserve name incorrectly (GH7458)
  • Bug in DatetimeIndex.intersection doesn’t preserve timezone (GH4690)
  • Bug in rolling_var where a window larger than the array would raise an error(GH7297)
  • Bug with last plotted timeseries dictating xlim (GH2960)
  • Bug with secondary_y axis not being considered for timeseries xlim (GH3490)
  • Bug in Float64Index assignment with a non scalar indexer (GH7586)
  • Bug in pandas.core.strings.str_contains does not properly match in a case insensitive fashion when regex=False and case=False (GH7505)
  • Bug in expanding_cov, expanding_corr, rolling_cov, and rolling_corr for two arguments with mismatched index (GH7512)
  • Bug in to_sql taking the boolean column as text column (GH7678)
  • Bug in grouped hist doesn’t handle rot kw and sharex kw properly (GH7234)
  • Bug in .loc performing fallback integer indexing with object dtype indices (GH7496)
  • Bug (regression) in PeriodIndex constructor when passed Series objects (GH7701).

v0.14.0 (May 31 , 2014)

This is a major release from 0.13.1 and includes a small number of API changes, several new features, enhancements, and performance improvements along with a large number of bug fixes. We recommend that all users upgrade to this version.


In 0.14.0 all NDFrame based containers have undergone significant internal refactoring. Before that each block of homogeneous data had its own labels and extra care was necessary to keep those in sync with the parent container’s labels. This should not have any visible user/API behavior changes (GH6745)

API changes

  • read_excel uses 0 as the default sheet (GH6573)

  • iloc will now accept out-of-bounds indexers for slices, e.g. a value that exceeds the length of the object being indexed. These will be excluded. This will make pandas conform more with python/numpy indexing of out-of-bounds values. A single indexer that is out-of-bounds and drops the dimensions of the object will still raise IndexError (GH6296, GH6299). This could result in an empty axis (e.g. an empty DataFrame being returned)

    In [1]: dfl = DataFrame(np.random.randn(5,2),columns=list('AB'))
    In [2]: dfl
              A         B
    0  1.583584 -0.438313
    1 -0.402537 -0.780572
    2 -0.141685  0.542241
    3  0.370966 -0.251642
    4  0.787484  1.666563
    In [3]: dfl.iloc[:,2:3]
    Empty DataFrame
    Columns: []
    Index: [0, 1, 2, 3, 4]
    In [4]: dfl.iloc[:,1:3]
    0 -0.438313
    1 -0.780572
    2  0.542241
    3 -0.251642
    4  1.666563
    In [5]: dfl.iloc[4:6]
              A         B
    4  0.787484  1.666563

    These are out-of-bounds selections

    IndexError: positional indexers are out-of-bounds
    IndexError: single positional indexer is out-of-bounds
  • Slicing with negative start, stop & step values handles corner cases better (GH6531):

    • df.iloc[:-len(df)] is now empty
    • df.iloc[len(df)::-1] now enumerates all elements in reverse
  • The DataFrame.interpolate() keyword downcast default has been changed from infer to None. This is to preseve the original dtype unless explicitly requested otherwise (GH6290).

  • When converting a dataframe to HTML it used to return Empty DataFrame. This special case has been removed, instead a header with the column names is returned (GH6062).

  • Series and Index now internall share more common operations, e.g. factorize(),nunique(),value_counts() are now supported on Index types as well. The Series.weekday property from is removed from Series for API consistency. Using a DatetimeIndex/PeriodIndex method on a Series will now raise a TypeError. (GH4551, GH4056, GH5519, GH6380, GH7206).

  • Add is_month_start, is_month_end, is_quarter_start, is_quarter_end, is_year_start, is_year_end accessors for DateTimeIndex / Timestamp which return a boolean array of whether the timestamp(s) are at the start/end of the month/quarter/year defined by the frequency of the DateTimeIndex / Timestamp (GH4565, GH6998)

  • Local variable usage has changed in pandas.eval()/DataFrame.eval()/DataFrame.query() (GH5987). For the DataFrame methods, two things have changed

    • Column names are now given precedence over locals
    • Local variables must be referred to explicitly. This means that even if you have a local variable that is not a column you must still refer to it with the '@' prefix.
    • You can have an expression like df.query('@a < a') with no complaints from pandas about ambiguity of the name a.
    • The top-level pandas.eval() function does not allow you use the '@' prefix and provides you with an error message telling you so.
    • NameResolutionError was removed because it isn’t necessary anymore.
  • Define and document the order of column vs index names in query/eval (GH6676)

  • concat will now concatenate mixed Series and DataFrames using the Series name or numbering columns as needed (GH2385). See the docs

  • Slicing and advanced/boolean indexing operations on Index classes as well as Index.delete() and Index.drop() methods will no longer change the type of the resulting index (GH6440, GH7040)

    In [6]: i = pd.Index([1, 2, 3, 'a' , 'b', 'c'])
    In [7]: i[[0,1,2]]
    Out[7]: Index([1, 2, 3], dtype='object')
    In [8]: i.drop(['a', 'b', 'c'])
    Out[8]: Index([1, 2, 3], dtype='object')

    Previously, the above operation would return Int64Index. If you’d like to do this manually, use Index.astype()

    In [9]: i[[0,1,2]].astype(np.int_)
    Out[9]: Int64Index([1, 2, 3], dtype='int32')
  • set_index no longer converts MultiIndexes to an Index of tuples. For example, the old behavior returned an Index in this case (GH6459):

    # Old behavior, casted MultiIndex to an Index
    In [10]: tuple_ind
    Out[10]: Index([(u'a', u'c'), (u'a', u'd'), (u'b', u'c'), (u'b', u'd')], dtype='object')
    In [11]: df_multi.set_index(tuple_ind)
                   0         1
    (a, c)  0.471435 -1.190976
    (a, d)  1.432707 -0.312652
    (b, c) -0.720589  0.887163
    (b, d)  0.859588 -0.636524
    # New behavior
    In [12]: mi
    MultiIndex(levels=[[u'a', u'b'], [u'c', u'd']],
               labels=[[0, 0, 1, 1], [0, 1, 0, 1]])
    In [13]: df_multi.set_index(mi)
                0         1
    a c  0.471435 -1.190976
      d  1.432707 -0.312652
    b c -0.720589  0.887163
      d  0.859588 -0.636524

    This also applies when passing multiple indices to set_index:

    # Old output, 2-level MultiIndex of tuples
    In [14]: df_multi.set_index([df_multi.index, df_multi.index])
                          0         1
    (a, c) (a, c)  0.471435 -1.190976
    (a, d) (a, d)  1.432707 -0.312652
    (b, c) (b, c) -0.720589  0.887163
    (b, d) (b, d)  0.859588 -0.636524
    # New output, 4-level MultiIndex
    In [15]: df_multi.set_index([df_multi.index, df_multi.index])
                    0         1
    a c a c  0.471435 -1.190976
      d a d  1.432707 -0.312652
    b c b c -0.720589  0.887163
      d b d  0.859588 -0.636524
  • pairwise keyword was added to the statistical moment functions rolling_cov, rolling_corr, ewmcov, ewmcorr, expanding_cov, expanding_corr to allow the calculation of moving window covariance and correlation matrices (GH4950). See Computing rolling pairwise covariances and correlations in the docs.

    In [16]: df = DataFrame(np.random.randn(10,4),columns=list('ABCD'))
    In [17]: covs = rolling_cov(df[['A','B','C']], df[['B','C','D']], 5, pairwise=True)
    In [18]: covs[df.index[-1]]
              B         C         D
    A  0.128104  0.183628 -0.047358
    B  0.856265  0.058945  0.145447
    C  0.058945  0.335350  0.390637
  • Series.iteritems() is now lazy (returns an iterator rather than a list). This was the documented behavior prior to 0.14. (GH6760)

  • Added nunique and value_counts functions to Index for counting unique elements. (GH6734)

  • stack and unstack now raise a ValueError when the level keyword refers to a non-unique item in the Index (previously raised a KeyError). (GH6738)

  • drop unused order argument from Series.sort; args now are in the same order as Series.order; add na_position arg to conform to Series.order (GH6847)

  • default sorting algorithm for Series.order is now quicksort, to conform with Series.sort (and numpy defaults)

  • add inplace keyword to Series.order/sort to make them inverses (GH6859)

  • DataFrame.sort now places NaNs at the beginning or end of the sort according to the na_position parameter. (GH3917)

  • accept TextFileReader in concat, which was affecting a common user idiom (GH6583), this was a regression from 0.13.1

  • Added factorize functions to Index and Series to get indexer and unique values (GH7090)

  • describe on a DataFrame with a mix of Timestamp and string like objects returns a different Index (GH7088). Previously the index was unintentionally sorted.

  • Arithmetic operations with only bool dtypes now give a warning indicating that they are evaluated in Python space for +, -, and * operations and raise for all others (GH7011, GH6762, GH7015, GH7210)

    x = pd.Series(np.random.rand(10) > 0.5)
    y = True
    x + y  # warning generated: should do x | y instead
    x / y  # this raises because it doesn't make sense
    NotImplementedError: operator '/' not implemented for bool dtypes
  • In HDFStore, select_as_multiple will always raise a KeyError, when a key or the selector is not found (GH6177)

  • df['col'] = value and df.loc[:,'col'] = value are now completely equivalent; previously the .loc would not necessarily coerce the dtype of the resultant series (GH6149)

  • dtypes and ftypes now return a series with dtype=object on empty containers (GH5740)

  • df.to_csv will now return a string of the CSV data if neither a target path nor a buffer is provided (GH6061)

  • pd.infer_freq() will now raise a TypeError if given an invalid Series/Index type (GH6407, GH6463)

  • A tuple passed to DataFame.sort_index will be interpreted as the levels of the index, rather than requiring a list of tuple (GH4370)

  • all offset operations now return Timestamp types (rather than datetime), Business/Week frequencies were incorrect (GH4069)

  • to_excel now converts np.inf into a string representation, customizable by the inf_rep keyword argument (Excel has no native inf representation) (GH6782)

  • Replace pandas.compat.scipy.scoreatpercentile with numpy.percentile (GH6810)

  • .quantile on a datetime[ns] series now returns Timestamp instead of np.datetime64 objects (GH6810)

  • change AssertionError to TypeError for invalid types passed to concat (GH6583)

  • Raise a TypeError when DataFrame is passed an iterator as the data argument (GH5357)

Display Changes

  • The default way of printing large DataFrames has changed. DataFrames exceeding max_rows and/or max_columns are now displayed in a centrally truncated view, consistent with the printing of a pandas.Series (GH5603).

    In previous versions, a DataFrame was truncated once the dimension constraints were reached and an ellipse (...) signaled that part of the data was cut off.

    The previous look of truncate.

    In the current version, large DataFrames are centrally truncated, showing a preview of head and tail in both dimensions.

    The new look.
  • allow option 'truncate' for display.show_dimensions to only show the dimensions if the frame is truncated (GH6547).

    The default for display.show_dimensions will now be truncate. This is consistent with how Series display length.

    In [19]: dfd = pd.DataFrame(np.arange(25).reshape(-1,5), index=[0,1,2,3,4], columns=[0,1,2,3,4])
    # show dimensions since this is truncated
    In [20]: with pd.option_context('display.max_rows', 2, 'display.max_columns', 2,
       ....:                        'display.show_dimensions', 'truncate'):
       ....:    print(dfd)
         0 ...   4
    0    0 ...   4
    ..  .. ...  ..
    4   20 ...  24
    [5 rows x 5 columns]
    # will not show dimensions since it is not truncated
    In [21]: with pd.option_context('display.max_rows', 10, 'display.max_columns', 40,
       ....:                        'display.show_dimensions', 'truncate'):
       ....:    print(dfd)
        0   1   2   3   4
    0   0   1   2   3   4
    1   5   6   7   8   9
    2  10  11  12  13  14
    3  15  16  17  18  19
    4  20  21  22  23  24
  • Regression in the display of a MultiIndexed Series with display.max_rows is less than the length of the series (GH7101)

  • Fixed a bug in the HTML repr of a truncated Series or DataFrame not showing the class name with the large_repr set to ‘info’ (GH7105)

  • The verbose keyword in, which controls whether to shorten the info representation, is now None by default. This will follow the global setting in display.max_info_columns. The global setting can be overriden with verbose=True or verbose=False.

  • Fixed a bug with the info repr not honoring the display.max_info_columns setting (GH6939)

  • Offset/freq info now in Timestamp __repr__ (GH4553)

Text Parsing API Changes

read_csv()/read_table() will now be noiser w.r.t invalid options rather than falling back to the PythonParser.

  • Raise ValueError when sep specified with delim_whitespace=True in read_csv()/read_table() (GH6607)
  • Raise ValueError when engine='c' specified with unsupported options in read_csv()/read_table() (GH6607)
  • Raise ValueError when fallback to python parser causes options to be ignored (GH6607)
  • Produce ParserWarning on fallback to python parser when no options are ignored (GH6607)
  • Translate sep='\s+' to delim_whitespace=True in read_csv()/read_table() if no other C-unsupported options specified (GH6607)

Groupby API Changes

More consistent behaviour for some groupby methods:

  • groupby head and tail now act more like filter rather than an aggregation:

    In [22]: df = pd.DataFrame([[1, 2], [1, 4], [5, 6]], columns=['A', 'B'])
    In [23]: g = df.groupby('A')
    In [24]: g.head(1)  # filters DataFrame
       A  B
    0  1  2
    2  5  6
    In [25]: g.apply(lambda x: x.head(1))  # used to simply fall-through
         A  B
    1 0  1  2
    5 2  5  6
  • groupby head and tail respect column selection:

    In [26]: g[['B']].head(1)
    0  2
    2  6
  • groupby nth now reduces by default; filtering can be achieved by passing as_index=False. With an optional dropna argument to ignore NaN. See the docs.


    In [27]: df = DataFrame([[1, np.nan], [1, 4], [5, 6]], columns=['A', 'B'])
    In [28]: g = df.groupby('A')
    In [29]: g.nth(0)
    1 NaN
    5   6
    # this is equivalent to g.first()
    In [30]: g.nth(0, dropna='any')
    1  4
    5  6
    # this is equivalent to g.last()
    In [31]: g.nth(-1, dropna='any')
    1  4
    5  6


    In [32]: gf = df.groupby('A',as_index=False)
    In [33]: gf.nth(0)
       A   B
    0  1 NaN
    2  5   6
    In [34]: gf.nth(0, dropna='any')
    1  4
    5  6
  • groupby will now not return the grouped column for non-cython functions (GH5610, GH5614, GH6732), as its already the index

    In [35]: df = DataFrame([[1, np.nan], [1, 4], [5, 6], [5, 8]], columns=['A', 'B'])
    In [36]: g = df.groupby('A')
    In [37]: g.count()
    1  1
    5  2
    In [38]: g.describe()
    1 count  1.000000
      mean   4.000000
      std         NaN
      min    4.000000
      25%    4.000000
      50%    4.000000
      75%    4.000000
    ...           ...
    5 mean   7.000000
      std    1.414214
      min    6.000000
      25%    6.500000
      50%    7.000000
      75%    7.500000
      max    8.000000
    [16 rows x 1 columns]
  • passing as_index will leave the grouped column in-place (this is not change in 0.14.0)

    In [39]: df = DataFrame([[1, np.nan], [1, 4], [5, 6], [5, 8]], columns=['A', 'B'])
    In [40]: g = df.groupby('A',as_index=False)
    In [41]: g.count()
       A  B
    0  1  1
    1  5  2
    In [42]: g.describe()
             A         B
    0 count  2  1.000000
      mean   1  4.000000
      std    0       NaN
      min    1  4.000000
      25%    1  4.000000
      50%    1  4.000000
      75%    1  4.000000
    ...     ..       ...
    1 mean   5  7.000000
      std    0  1.414214
      min    5  6.000000
      25%    5  6.500000
      50%    5  7.000000
      75%    5  7.500000
      max    5  8.000000
    [16 rows x 2 columns]
  • Allow specification of a more complex groupby via pd.Grouper, such as grouping by a Time and a string field simultaneously. See the docs. (GH3794)

  • Better propagation/preservation of Series names when performing groupby operations:

    • SeriesGroupBy.agg will ensure that the name attribute of the original series is propagated to the result (GH6265).
    • If the function provided to GroupBy.apply returns a named series, the name of the series will be kept as the name of the column index of the DataFrame returned by GroupBy.apply (GH6124). This facilitates DataFrame.stack operations where the name of the column index is used as the name of the inserted column containing the pivoted data.


The SQL reading and writing functions now support more database flavors through SQLAlchemy (GH2717, GH4163, GH5950, GH6292). All databases supported by SQLAlchemy can be used, such as PostgreSQL, MySQL, Oracle, Microsoft SQL server (see documentation of SQLAlchemy on included dialects).

The functionality of providing DBAPI connection objects will only be supported for sqlite3 in the future. The 'mysql' flavor is deprecated.

The new functions read_sql_query() and read_sql_table() are introduced. The function read_sql() is kept as a convenience wrapper around the other two and will delegate to specific function depending on the provided input (database table name or sql query).

In practice, you have to provide a SQLAlchemy engine to the sql functions. To connect with SQLAlchemy you use the create_engine() function to create an engine object from database URI. You only need to create the engine once per database you are connecting to. For an in-memory sqlite database:

In [43]: from sqlalchemy import create_engine

# Create your connection.
In [44]: engine = create_engine('sqlite:///:memory:')

This engine can then be used to write or read data to/from this database:

In [45]: df = pd.DataFrame({'A': [1,2,3], 'B': ['a', 'b', 'c']})

In [46]: df.to_sql('db_table', engine, index=False)

You can read data from a database by specifying the table name:

In [47]: pd.read_sql_table('db_table', engine)
   A  B
0  1  a
1  2  b
2  3  c

or by specifying a sql query:

In [48]: pd.read_sql_query('SELECT * FROM db_table', engine)
   A  B
0  1  a
1  2  b
2  3  c

Some other enhancements to the sql functions include:

  • support for writing the index. This can be controlled with the index keyword (default is True).
  • specify the column label to use when writing the index with index_label.
  • specify string columns to parse as datetimes withh the parse_dates keyword in read_sql_query() and read_sql_table().


Some of the existing functions or function aliases have been deprecated and will be removed in future versions. This includes: tquery, uquery, read_frame, frame_query, write_frame.


The support for the ‘mysql’ flavor when using DBAPI connection objects has been deprecated. MySQL will be further supported with SQLAlchemy engines (GH6900).

MultiIndexing Using Slicers

In 0.14.0 we added a new way to slice multi-indexed objects. You can slice a multi-index by providing multiple indexers.

You can provide any of the selectors as if you are indexing by label, see Selection by Label, including slices, lists of labels, labels, and boolean indexers.

You can use slice(None) to select all the contents of that level. You do not need to specify all the deeper levels, they will be implied as slice(None).

As usual, both sides of the slicers are included as this is label indexing.

See the docs See also issues (GH6134, GH4036, GH3057, GH2598, GH5641, GH7106)


You should specify all axes in the .loc specifier, meaning the indexer for the index and for the columns. Their are some ambiguous cases where the passed indexer could be mis-interpreted as indexing both axes, rather than into say the MuliIndex for the rows.

You should do this:


rather than this:



You will need to make sure that the selection axes are fully lexsorted!

In [49]: def mklbl(prefix,n):
   ....:     return ["%s%s" % (prefix,i)  for i in range(n)]

In [50]: index = MultiIndex.from_product([mklbl('A',4),
   ....:                                  mklbl('B',2),
   ....:                                  mklbl('C',4),
   ....:                                  mklbl('D',2)])

In [51]: columns = MultiIndex.from_tuples([('a','foo'),('a','bar'),
   ....:                                   ('b','foo'),('b','bah')],
   ....:                                    names=['lvl0', 'lvl1'])

In [52]: df = DataFrame(np.arange(len(index)*len(columns)).reshape((len(index),len(columns))),
   ....:                index=index,
   ....:                columns=columns).sortlevel().sortlevel(axis=1)

In [53]: df
lvl0           a         b     
lvl1         bar  foo  bah  foo
A0 B0 C0 D0    1    0    3    2
         D1    5    4    7    6
      C1 D0    9    8   11   10
         D1   13   12   15   14
      C2 D0   17   16   19   18
         D1   21   20   23   22
      C3 D0   25   24   27   26
...          ...  ...  ...  ...
A3 B1 C0 D1  229  228  231  230
      C1 D0  233  232  235  234
         D1  237  236  239  238
      C2 D0  241  240  243  242
         D1  245  244  247  246
      C3 D0  249  248  251  250
         D1  253  252  255  254

[64 rows x 4 columns]

Basic multi-index slicing using slices, lists, and labels.

In [54]: df.loc[(slice('A1','A3'),slice(None), ['C1','C3']),:]
lvl0           a         b     
lvl1         bar  foo  bah  foo
A1 B0 C1 D0   73   72   75   74
         D1   77   76   79   78
      C3 D0   89   88   91   90
         D1   93   92   95   94
   B1 C1 D0  105  104  107  106
         D1  109  108  111  110
      C3 D0  121  120  123  122
...          ...  ...  ...  ...
A3 B0 C1 D1  205  204  207  206
      C3 D0  217  216  219  218
         D1  221  220  223  222
   B1 C1 D0  233  232  235  234
         D1  237  236  239  238
      C3 D0  249  248  251  250
         D1  253  252  255  254

[24 rows x 4 columns]

You can use a pd.IndexSlice to shortcut the creation of these slices

In [55]: idx = pd.IndexSlice

In [56]: df.loc[idx[:,:,['C1','C3']],idx[:,'foo']]
lvl0           a    b
lvl1         foo  foo
A0 B0 C1 D0    8   10
         D1   12   14
      C3 D0   24   26
         D1   28   30
   B1 C1 D0   40   42
         D1   44   46
      C3 D0   56   58
...          ...  ...
A3 B0 C1 D1  204  206
      C3 D0  216  218
         D1  220  222
   B1 C1 D0  232  234
         D1  236  238
      C3 D0  248  250
         D1  252  254

[32 rows x 2 columns]

It is possible to perform quite complicated selections using this method on multiple axes at the same time.

In [57]: df.loc['A1',(slice(None),'foo')]
lvl0        a    b
lvl1      foo  foo
B0 C0 D0   64   66
      D1   68   70
   C1 D0   72   74
      D1   76   78
   C2 D0   80   82
      D1   84   86
   C3 D0   88   90
...       ...  ...
B1 C0 D1  100  102
   C1 D0  104  106
      D1  108  110
   C2 D0  112  114
      D1  116  118
   C3 D0  120  122
      D1  124  126

[16 rows x 2 columns]

In [58]: df.loc[idx[:,:,['C1','C3']],idx[:,'foo']]
lvl0           a    b
lvl1         foo  foo
A0 B0 C1 D0    8   10
         D1   12   14
      C3 D0   24   26
         D1   28   30
   B1 C1 D0   40   42
         D1   44   46
      C3 D0   56   58
...          ...  ...
A3 B0 C1 D1  204  206
      C3 D0  216  218
         D1  220  222
   B1 C1 D0  232  234
         D1  236  238
      C3 D0  248  250
         D1  252  254

[32 rows x 2 columns]

Using a boolean indexer you can provide selection related to the values.

In [59]: mask = df[('a','foo')]>200

In [60]: df.loc[idx[mask,:,['C1','C3']],idx[:,'foo']]
lvl0           a    b
lvl1         foo  foo
A3 B0 C1 D1  204  206
      C3 D0  216  218
         D1  220  222
   B1 C1 D0  232  234
         D1  236  238
      C3 D0  248  250
         D1  252  254

You can also specify the axis argument to .loc to interpret the passed slicers on a single axis.

In [61]: df.loc(axis=0)[:,:,['C1','C3']]
lvl0           a         b     
lvl1         bar  foo  bah  foo
A0 B0 C1 D0    9    8   11   10
         D1   13   12   15   14
      C3 D0   25   24   27   26
         D1   29   28   31   30
   B1 C1 D0   41   40   43   42
         D1   45   44   47   46
      C3 D0   57   56   59   58
...          ...  ...  ...  ...
A3 B0 C1 D1  205  204  207  206
      C3 D0  217  216  219  218
         D1  221  220  223  222
   B1 C1 D0  233  232  235  234
         D1  237  236  239  238
      C3 D0  249  248  251  250
         D1  253  252  255  254

[32 rows x 4 columns]

Furthermore you can set the values using these methods

In [62]: df2 = df.copy()

In [63]: df2.loc(axis=0)[:,:,['C1','C3']] = -10

In [64]: df2
lvl0           a         b     
lvl1         bar  foo  bah  foo
A0 B0 C0 D0    1    0    3    2
         D1    5    4    7    6
      C1 D0  -10  -10  -10  -10
         D1  -10  -10  -10  -10
      C2 D0   17   16   19   18
         D1   21   20   23   22
      C3 D0  -10  -10  -10  -10
...          ...  ...  ...  ...
A3 B1 C0 D1  229  228  231  230
      C1 D0  -10  -10  -10  -10
         D1  -10  -10  -10  -10
      C2 D0  241  240  243  242
         D1  245  244  247  246
      C3 D0  -10  -10  -10  -10
         D1  -10  -10  -10  -10

[64 rows x 4 columns]

You can use a right-hand-side of an alignable object as well.

In [65]: df2 = df.copy()

In [66]: df2.loc[idx[:,:,['C1','C3']],:] = df2*1000

In [67]: df2
lvl0              a               b        
lvl1            bar     foo     bah     foo
A0 B0 C0 D0       1       0       3       2
         D1       5       4       7       6
      C1 D0    9000    8000   11000   10000
         D1   13000   12000   15000   14000
      C2 D0      17      16      19      18
         D1      21      20      23      22
      C3 D0   25000   24000   27000   26000
...             ...     ...     ...     ...
A3 B1 C0 D1     229     228     231     230
      C1 D0  233000  232000  235000  234000
         D1  237000  236000  239000  238000
      C2 D0     241     240     243     242
         D1     245     244     247     246
      C3 D0  249000  248000  251000  250000
         D1  253000  252000  255000  254000

[64 rows x 4 columns]


  • Hexagonal bin plots from DataFrame.plot with kind='hexbin' (GH5478), See the docs.

  • DataFrame.plot and Series.plot now supports area plot with specifying kind='area' (GH6656), See the docs

  • Pie plots from Series.plot and DataFrame.plot with kind='pie' (GH6976), See the docs.

  • Plotting with Error Bars is now supported in the .plot method of DataFrame and Series objects (GH3796, GH6834), See the docs.

  • DataFrame.plot and Series.plot now support a table keyword for plotting matplotlib.Table, See the docs. The table keyword can receive the following values.

    • False: Do nothing (default).
    • True: Draw a table using the DataFrame or Series called plot method. Data will be transposed to meet matplotlib’s default layout.
    • DataFrame or Series: Draw matplotlib.table using the passed data. The data will be drawn as displayed in print method (not transposed automatically). Also, helper function is added to create a table from DataFrame and Series, and add it to an matplotlib.Axes.
  • plot(legend='reverse') will now reverse the order of legend labels for most plot kinds. (GH6014)

  • Line plot and area plot can be stacked by stacked=True (GH6656)

  • Following keywords are now acceptable for DataFrame.plot() with kind='bar' and kind='barh':

    • width: Specify the bar width. In previous versions, static value 0.5 was passed to matplotlib and it cannot be overwritten. (GH6604)
    • align: Specify the bar alignment. Default is center (different from matplotlib). In previous versions, pandas passes align=’edge’ to matplotlib and adjust the location to center by itself, and it results align keyword is not applied as expected. (GH4525)
    • position: Specify relative alignments for bar plot layout. From 0 (left/bottom-end) to 1(right/top-end). Default is 0.5 (center). (GH6604)

    Because of the default align value changes, coordinates of bar plots are now located on integer values (0.0, 1.0, 2.0 ...). This is intended to make bar plot be located on the same coodinates as line plot. However, bar plot may differs unexpectedly when you manually adjust the bar location or drawing area, such as using set_xlim, set_ylim, etc. In this cases, please modify your script to meet with new coordinates.

  • The parallel_coordinates() function now takes argument color instead of colors. A FutureWarning is raised to alert that the old colors argument will not be supported in a future release. (GH6956)

  • The parallel_coordinates() and andrews_curves() functions now take positional argument frame instead of data. A FutureWarning is raised if the old data argument is used by name. (GH6956)

  • DataFrame.boxplot() now supports layout keyword (GH6769)

  • DataFrame.boxplot() has a new keyword argument, return_type. It accepts 'dict', 'axes', or 'both', in which case a namedtuple with the matplotlib axes and a dict of matplotlib Lines is returned.

Prior Version Deprecations/Changes

There are prior version deprecations that are taking effect as of 0.14.0.


  • The pivot_table()/DataFrame.pivot_table() and crosstab() functions now take arguments index and columns instead of rows and cols. A FutureWarning is raised to alert that the old rows and cols arguments will not be supported in a future release (GH5505)

  • The DataFrame.drop_duplicates() and DataFrame.duplicated() methods now take argument subset instead of cols to better align with DataFrame.dropna(). A FutureWarning is raised to alert that the old cols arguments will not be supported in a future release (GH6680)

  • The DataFrame.to_csv() and DataFrame.to_excel() functions now takes argument columns instead of cols. A FutureWarning is raised to alert that the old cols arguments will not be supported in a future release (GH6645)

  • Indexers will warn FutureWarning when used with a scalar indexer and a non-floating point Index (GH4892, GH6960)

    # non-floating point indexes can only be indexed by integers / labels
    In [1]: Series(1,np.arange(5))[3.0]
            pandas/core/ FutureWarning: scalar indexers for index type Int64Index should be integers and not floating point
    Out[1]: 1
    In [2]: Series(1,np.arange(5)).iloc[3.0]
            pandas/core/ FutureWarning: scalar indexers for index type Int64Index should be integers and not floating point
    Out[2]: 1
    In [3]: Series(1,np.arange(5)).iloc[3.0:4]
            pandas/core/ FutureWarning: slice indexers when using iloc should be integers and not floating point
            3    1
            dtype: int64
    # these are Float64Indexes, so integer or floating point is acceptable
    In [4]: Series(1,np.arange(5.))[3]
    Out[4]: 1
    In [5]: Series(1,np.arange(5.))[3.0]
    Out[6]: 1
  • Numpy 1.9 compat w.r.t. deprecation warnings (GH6960)

  • Panel.shift() now has a function signature that matches DataFrame.shift(). The old positional argument lags has been changed to a keyword argument periods with a default value of 1. A FutureWarning is raised if the old argument lags is used by name. (GH6910)

  • The order keyword argument of factorize() will be removed. (GH6926).

  • Remove the copy keyword from DataFrame.xs(), Panel.major_xs(), Panel.minor_xs(). A view will be returned if possible, otherwise a copy will be made. Previously the user could think that copy=False would ALWAYS return a view. (GH6894)

  • The parallel_coordinates() function now takes argument color instead of colors. A FutureWarning is raised to alert that the old colors argument will not be supported in a future release. (GH6956)

  • The parallel_coordinates() and andrews_curves() functions now take positional argument frame instead of data. A FutureWarning is raised if the old data argument is used by name. (GH6956)

  • The support for the ‘mysql’ flavor when using DBAPI connection objects has been deprecated. MySQL will be further supported with SQLAlchemy engines (GH6900).

  • The following io.sql functions have been deprecated: tquery, uquery, read_frame, frame_query, write_frame.

  • The percentile_width keyword argument in describe() has been deprecated. Use the percentiles keyword instead, which takes a list of percentiles to display. The default output is unchanged.

  • The default return type of boxplot() will change from a dict to a matpltolib Axes in a future release. You can use the future behavior now by passing return_type='axes' to boxplot.

Known Issues

  • OpenPyXL 2.0.0 breaks backwards compatibility (GH7169)


  • DataFrame and Series will create a MultiIndex object if passed a tuples dict, See the docs (GH3323)

    In [68]: Series({('a', 'b'): 1, ('a', 'a'): 0,
       ....:         ('a', 'c'): 2, ('b', 'a'): 3, ('b', 'b'): 4})
    a  a    0
       b    1
       c    2
    b  a    3
       b    4
    dtype: int64
    In [69]: DataFrame({('a', 'b'): {('A', 'B'): 1, ('A', 'C'): 2},
       ....:            ('a', 'a'): {('A', 'C'): 3, ('A', 'B'): 4},
       ....:            ('a', 'c'): {('A', 'B'): 5, ('A', 'C'): 6},
       ....:            ('b', 'a'): {('A', 'C'): 7, ('A', 'B'): 8},
       ....:            ('b', 'b'): {('A', 'D'): 9, ('A', 'B'): 10}})
          a           b    
          a   b   c   a   b
    A B   4   1   5   8  10
      C   3   2   6   7 NaN
      D NaN NaN NaN NaN   9
  • Added the sym_diff method to Index (GH5543)

  • DataFrame.to_latex now takes a longtable keyword, which if True will return a table in a longtable environment. (GH6617)

  • Add option to turn off escaping in DataFrame.to_latex (GH6472)

  • pd.read_clipboard will, if the keyword sep is unspecified, try to detect data copied from a spreadsheet and parse accordingly. (GH6223)

  • Joining a singly-indexed DataFrame with a multi-indexed DataFrame (GH3662)

    See the docs. Joining multi-index DataFrames on both the left and right is not yet supported ATM.

    In [70]: household = DataFrame(dict(household_id = [1,2,3],
       ....:                            male = [0,1,0],
       ....:                            wealth = [196087.3,316478.7,294750]),
       ....:                       columns = ['household_id','male','wealth']
       ....:                      ).set_index('household_id')
    In [71]: household
                  male    wealth
    1                0  196087.3
    2                1  316478.7
    3                0  294750.0
    In [72]: portfolio = DataFrame(dict(household_id = [1,2,2,3,3,3,4],
       ....:                            asset_id = ["nl0000301109","nl0000289783","gb00b03mlx29",
       ....:                                        "gb00b03mlx29","lu0197800237","nl0000289965",np.nan],
       ....:                            name = ["ABN Amro","Robeco","Royal Dutch Shell","Royal Dutch Shell",
       ....:                                    "AAB Eastern Europe Equity Fund","Postbank BioTech Fonds",np.nan],
       ....:                            share = [1.0,0.4,0.6,0.15,0.6,0.25,1.0]),
       ....:                       columns = ['household_id','asset_id','name','share']
       ....:                      ).set_index(['household_id','asset_id'])
    In [73]: portfolio
                                                         name  share
    household_id asset_id                                           
    1            nl0000301109                        ABN Amro   1.00
    2            nl0000289783                          Robeco   0.40
                 gb00b03mlx29               Royal Dutch Shell   0.60
    3            gb00b03mlx29               Royal Dutch Shell   0.15
                 lu0197800237  AAB Eastern Europe Equity Fund   0.60
                 nl0000289965          Postbank BioTech Fonds   0.25
    4            NaN                                      NaN   1.00
    In [74]: household.join(portfolio, how='inner')
                               male    wealth                            name  \
    household_id asset_id                                                       
    1            nl0000301109     0  196087.3                        ABN Amro   
    2            nl0000289783     1  316478.7                          Robeco   
                 gb00b03mlx29     1  316478.7               Royal Dutch Shell   
    3            gb00b03mlx29     0  294750.0               Royal Dutch Shell   
                 lu0197800237     0  294750.0  AAB Eastern Europe Equity Fund   
                 nl0000289965     0  294750.0          Postbank BioTech Fonds   
    household_id asset_id             
    1            nl0000301109   1.00  
    2            nl0000289783   0.40  
                 gb00b03mlx29   0.60  
    3            gb00b03mlx29   0.15  
                 lu0197800237   0.60  
                 nl0000289965   0.25  
  • quotechar, doublequote, and escapechar can now be specified when using DataFrame.to_csv (GH5414, GH4528)

  • Partially sort by only the specified levels of a MultiIndex with the sort_remaining boolean kwarg. (GH3984)

  • Added to_julian_date to TimeStamp and DatetimeIndex. The Julian Date is used primarily in astronomy and represents the number of days from noon, January 1, 4713 BC. Because nanoseconds are used to define the time in pandas the actual range of dates that you can use is 1678 AD to 2262 AD. (GH4041)

  • DataFrame.to_stata will now check data for compatibility with Stata data types and will upcast when needed. When it is not possible to losslessly upcast, a warning is issued (GH6327)

  • DataFrame.to_stata and StataWriter will accept keyword arguments time_stamp and data_label which allow the time stamp and dataset label to be set when creating a file. (GH6545)

  • now handles reading unicode strings properly. (GH5940)

  • Holidays Calendars are now available and can be used with the CustomBusinessDay offset (GH6719)

  • Float64Index is now backed by a float64 dtype ndarray instead of an object dtype array (GH6471).

  • Implemented Panel.pct_change (GH6904)

  • Added how option to rolling-moment functions to dictate how to handle resampling; rolling_max() defaults to max, rolling_min() defaults to min, and all others default to mean (GH6297)

  • CustomBuisnessMonthBegin and CustomBusinessMonthEnd are now available (GH6866)

  • Series.quantile() and DataFrame.quantile() now accept an array of quantiles.

  • describe() now accepts an array of percentiles to include in the summary statistics (GH4196)

  • pivot_table can now accept Grouper by index and columns keywords (GH6913)

    In [75]: import datetime
    In [76]: df = DataFrame({
       ....:   'Branch' : 'A A A A A B'.split(),
       ....:   'Buyer': 'Carl Mark Carl Carl Joe Joe'.split(),
       ....:   'Quantity': [1, 3, 5, 1, 8, 1],
       ....:   'Date' : [datetime.datetime(2013,11,1,13,0), datetime.datetime(2013,9,1,13,5),
       ....:             datetime.datetime(2013,10,1,20,0), datetime.datetime(2013,10,2,10,0),
       ....:             datetime.datetime(2013,11,1,20,0), datetime.datetime(2013,10,2,10,0)],
       ....:   'PayDay' : [datetime.datetime(2013,10,4,0,0), datetime.datetime(2013,10,15,13,5),
       ....:               datetime.datetime(2013,9,5,20,0), datetime.datetime(2013,11,2,10,0),
       ....:               datetime.datetime(2013,10,7,20,0), datetime.datetime(2013,9,5,10,0)]})
    In [77]: df
      Branch Buyer                Date              PayDay  Quantity
    0      A  Carl 2013-11-01 13:00:00 2013-10-04 00:00:00         1
    1      A  Mark 2013-09-01 13:05:00 2013-10-15 13:05:00         3
    2      A  Carl 2013-10-01 20:00:00 2013-09-05 20:00:00         5
    3      A  Carl 2013-10-02 10:00:00 2013-11-02 10:00:00         1
    4      A   Joe 2013-11-01 20:00:00 2013-10-07 20:00:00         8
    5      B   Joe 2013-10-02 10:00:00 2013-09-05 10:00:00         1
    In [78]: pivot_table(df, index=Grouper(freq='M', key='Date'),
       ....:             columns=Grouper(freq='M', key='PayDay'),
       ....:             values='Quantity', aggfunc=np.sum)
    PayDay      2013-09-30  2013-10-31  2013-11-30
    2013-09-30         NaN           3         NaN
    2013-10-31           6         NaN           1
    2013-11-30         NaN           9         NaN
  • Arrays of strings can be wrapped to a specified width (str.wrap) (GH6999)

  • Add nsmallest() and Series.nlargest() methods to Series, See the docs (GH3960)

  • PeriodIndex fully supports partial string indexing like DatetimeIndex (GH7043)

    In [79]: prng = period_range('2013-01-01 09:00', periods=100, freq='H')
    In [80]: ps = Series(np.random.randn(len(prng)), index=prng)
    In [81]: ps
    2013-01-01 09:00    0.755414
    2013-01-01 10:00    0.215269
    2013-01-01 11:00    0.841009
    2013-01-01 12:00   -1.445810
    2013-01-01 13:00   -1.401973
    2013-01-01 14:00   -0.100918
    2013-01-01 15:00   -0.548242
    2013-01-05 06:00   -0.379811
    2013-01-05 07:00    0.702562
    2013-01-05 08:00   -0.850346
    2013-01-05 09:00    1.176812
    2013-01-05 10:00   -0.524336
    2013-01-05 11:00    0.700908
    2013-01-05 12:00    0.984188
    Freq: H, dtype: float64
    In [82]: ps['2013-01-02']
    2013-01-02 00:00   -0.208499
    2013-01-02 01:00    1.033801
    2013-01-02 02:00   -2.400454
    2013-01-02 03:00    2.030604
    2013-01-02 04:00   -1.142631
    2013-01-02 05:00    0.211883
    2013-01-02 06:00    0.704721
    2013-01-02 17:00    0.464392
    2013-01-02 18:00   -3.563517
    2013-01-02 19:00    1.321106
    2013-01-02 20:00    0.152631
    2013-01-02 21:00    0.164530
    2013-01-02 22:00   -0.430096
    2013-01-02 23:00    0.767369
    Freq: H, dtype: float64
  • read_excel can now read milliseconds in Excel dates and times with xlrd >= 0.9.3. (GH5945)

  • pd.stats.moments.rolling_var now uses Welford’s method for increased numerical stability (GH6817)

  • pd.expanding_apply and pd.rolling_apply now take args and kwargs that are passed on to the func (GH6289)

  • DataFrame.rank() now has a percentage rank option (GH5971)

  • Series.rank() now has a percentage rank option (GH5971)

  • Series.rank() and DataFrame.rank() now accept method='dense' for ranks without gaps (GH6514)

  • Support passing encoding with xlwt (GH3710)

  • Refactor Block classes removing Block.items attributes to avoid duplication in item handling (GH6745, GH6988).

  • Testing statements updated to use specialized asserts (GH6175)


  • Performance improvement when converting DatetimeIndex to floating ordinals using DatetimeConverter (GH6636)
  • Performance improvement for DataFrame.shift (GH5609)
  • Performance improvement in indexing into a multi-indexed Series (GH5567)
  • Performance improvements in single-dtyped indexing (GH6484)
  • Improve performance of DataFrame construction with certain offsets, by removing faulty caching (e.g. MonthEnd,BusinessMonthEnd), (GH6479)
  • Improve performance of CustomBusinessDay (GH6584)
  • improve performance of slice indexing on Series with string keys (GH6341, GH6372)
  • Performance improvement for DataFrame.from_records when reading a specified number of rows from an iterable (GH6700)
  • Performance improvements in timedelta conversions for integer dtypes (GH6754)
  • Improved performance of compatible pickles (GH6899)
  • Improve performance in certain reindexing operations by optimizing take_2d (GH6749)
  • GroupBy.count() is now implemented in Cython and is much faster for large numbers of groups (GH7016).


There are no experimental changes in 0.14.0

Bug Fixes

  • Bug in Series ValueError when index doesn’t match data (GH6532)
  • Prevent segfault due to MultiIndex not being supported in HDFStore table format (GH1848)
  • Bug in pd.DataFrame.sort_index where mergesort wasn’t stable when ascending=False (GH6399)
  • Bug in pd.tseries.frequencies.to_offset when argument has leading zeroes (GH6391)
  • Bug in version string gen. for dev versions with shallow clones / install from tarball (GH6127)
  • Inconsistent tz parsing Timestamp / to_datetime for current year (GH5958)
  • Indexing bugs with reordered indexes (GH6252, GH6254)
  • Bug in .xs with a Series multiindex (GH6258, GH5684)
  • Bug in conversion of a string types to a DatetimeIndex with a specified frequency (GH6273, GH6274)
  • Bug in eval where type-promotion failed for large expressions (GH6205)
  • Bug in interpolate with inplace=True (GH6281)
  • HDFStore.remove now handles start and stop (GH6177)
  • HDFStore.select_as_multiple handles start and stop the same way as select (GH6177)
  • HDFStore.select_as_coordinates and select_column works with a where clause that results in filters (GH6177)
  • Regression in join of non_unique_indexes (GH6329)
  • Issue with groupby agg with a single function and a a mixed-type frame (GH6337)
  • Bug in DataFrame.replace() when passing a non- bool to_replace argument (GH6332)
  • Raise when trying to align on different levels of a multi-index assignment (GH3738)
  • Bug in setting complex dtypes via boolean indexing (GH6345)
  • Bug in TimeGrouper/resample when presented with a non-monotonic DatetimeIndex that would return invalid results. (GH4161)
  • Bug in index name propogation in TimeGrouper/resample (GH4161)
  • TimeGrouper has a more compatible API to the rest of the groupers (e.g. groups was missing) (GH3881)
  • Bug in multiple grouping with a TimeGrouper depending on target column order (GH6764)
  • Bug in pd.eval when parsing strings with possible tokens like '&' (GH6351)
  • Bug correctly handle placements of -inf in Panels when dividing by integer 0 (GH6178)
  • DataFrame.shift with axis=1 was raising (GH6371)
  • Disabled clipboard tests until release time (run locally with nosetests -A disabled) (GH6048).
  • Bug in DataFrame.replace() when passing a nested dict that contained keys not in the values to be replaced (GH6342)
  • str.match ignored the na flag (GH6609).
  • Bug in take with duplicate columns that were not consolidated (GH6240)
  • Bug in interpolate changing dtypes (GH6290)
  • Bug in Series.get, was using a buggy access method (GH6383)
  • Bug in hdfstore queries of the form where=[('date', '>=', datetime(2013,1,1)), ('date', '<=', datetime(2014,1,1))] (GH6313)
  • Bug in DataFrame.dropna with duplicate indices (GH6355)
  • Regression in chained getitem indexing with embedded list-like from 0.12 (GH6394)
  • Float64Index with nans not comparing correctly (GH6401)
  • eval/query expressions with strings containing the @ character will now work (GH6366).
  • Bug in Series.reindex when specifying a method with some nan values was inconsistent (noted on a resample) (GH6418)
  • Bug in DataFrame.replace() where nested dicts were erroneously depending on the order of dictionary keys and values (GH5338).
  • Perf issue in concatting with empty objects (GH3259)
  • Clarify sorting of sym_diff on Index objects with NaN values (GH6444)
  • Regression in MultiIndex.from_product with a DatetimeIndex as input (GH6439)
  • Bug in str.extract when passed a non-default index (GH6348)
  • Bug in str.split when passed pat=None and n=1 (GH6466)
  • Bug in when passed "F-F_Momentum_Factor" and data_source="famafrench" (GH6460)
  • Bug in sum of a timedelta64[ns] series (GH6462)
  • Bug in resample with a timezone and certain offsets (GH6397)
  • Bug in iat/iloc with duplicate indices on a Series (GH6493)
  • Bug in read_html where nan’s were incorrectly being used to indicate missing values in text. Should use the empty string for consistency with the rest of pandas (GH5129).
  • Bug in read_html tests where redirected invalid URLs would make one test fail (GH6445).
  • Bug in multi-axis indexing using .loc on non-unique indices (GH6504)
  • Bug that caused _ref_locs corruption when slice indexing across columns axis of a DataFrame (GH6525)
  • Regression from 0.13 in the treatment of numpy datetime64 non-ns dtypes in Series creation (GH6529)
  • .names attribute of MultiIndexes passed to set_index are now preserved (GH6459).
  • Bug in setitem with a duplicate index and an alignable rhs (GH6541)
  • Bug in setitem with .loc on mixed integer Indexes (GH6546)
  • Bug in pd.read_stata which would use the wrong data types and missing values (GH6327)
  • Bug in DataFrame.to_stata that lead to data loss in certain cases, and could be exported using the wrong data types and missing values (GH6335)
  • StataWriter replaces missing values in string columns by empty string (GH6802)
  • Inconsistent types in Timestamp addition/subtraction (GH6543)
  • Bug in preserving frequency across Timestamp addition/subtraction (GH4547)
  • Bug in empty list lookup caused IndexError exceptions (GH6536, GH6551)
  • Series.quantile raising on an object dtype (GH6555)
  • Bug in .xs with a nan in level when dropped (GH6574)
  • Bug in fillna with method='bfill/ffill' and datetime64[ns] dtype (GH6587)
  • Bug in sql writing with mixed dtypes possibly leading to data loss (GH6509)
  • Bug in Series.pop (GH6600)
  • Bug in iloc indexing when positional indexer matched Int64Index of the corresponding axis and no reordering happened (GH6612)
  • Bug in fillna with limit and value specified
  • Bug in DataFrame.to_stata when columns have non-string names (GH4558)
  • Bug in compat with np.compress, surfaced in (GH6658)
  • Bug in binary operations with a rhs of a Series not aligning (GH6681)
  • Bug in DataFrame.to_stata which incorrectly handles nan values and ignores with_index keyword argument (GH6685)
  • Bug in resample with extra bins when using an evenly divisible frequency (GH4076)
  • Bug in consistency of groupby aggregation when passing a custom function (GH6715)
  • Bug in resample when how=None resample freq is the same as the axis frequency (GH5955)
  • Bug in downcasting inference with empty arrays (GH6733)
  • Bug in obj.blocks on sparse containers dropping all but the last items of same for dtype (GH6748)
  • Bug in unpickling NaT (NaTType) (GH4606)
  • Bug in DataFrame.replace() where regex metacharacters were being treated as regexs even when regex=False (GH6777).
  • Bug in timedelta ops on 32-bit platforms (GH6808)
  • Bug in setting a tz-aware index directly via .index (GH6785)
  • Bug in where numexpr would try to evaluate arithmetic ops (GH6762).
  • Bug in Makefile where it didn’t remove Cython generated C files with make clean (GH6768)
  • Bug with numpy < 1.7.2 when reading long strings from HDFStore (GH6166)
  • Bug in DataFrame._reduce where non bool-like (0/1) integers were being coverted into bools. (GH6806)
  • Regression from 0.13 with fillna and a Series on datetime-like (GH6344)
  • Bug in adding np.timedelta64 to DatetimeIndex with timezone outputs incorrect results (GH6818)
  • Bug in DataFrame.replace() where changing a dtype through replacement would only replace the first occurrence of a value (GH6689)
  • Better error message when passing a frequency of ‘MS’ in Period construction (GH5332)
  • Bug in Series.__unicode__ when max_rows=None and the Series has more than 1000 rows. (GH6863)
  • Bug in groupby.get_group where a datetlike wasn’t always accepted (GH5267)
  • Bug in groupBy.get_group created by TimeGrouper raises AttributeError (GH6914)
  • Bug in DatetimeIndex.tz_localize and DatetimeIndex.tz_convert converting NaT incorrectly (GH5546)
  • Bug in arithmetic operations affecting NaT (GH6873)
  • Bug in Series.str.extract where the resulting Series from a single group match wasn’t renamed to the group name
  • Bug in DataFrame.to_csv where setting index=False ignored the header kwarg (GH6186)
  • Bug in DataFrame.plot and Series.plot, where the legend behave inconsistently when plotting to the same axes repeatedly (GH6678)
  • Internal tests for patching __finalize__ / bug in merge not finalizing (GH6923, GH6927)
  • accept TextFileReader in concat, which was affecting a common user idiom (GH6583)
  • Bug in C parser with leading whitespace (GH3374)
  • Bug in C parser with delim_whitespace=True and \r-delimited lines
  • Bug in python parser with explicit multi-index in row following column header (GH6893)
  • Bug in Series.rank and DataFrame.rank that caused small floats (<1e-13) to all receive the same rank (GH6886)
  • Bug in DataFrame.apply with functions that used *args`` or **kwargs and returned an empty result (GH6952)
  • Bug in sum/mean on 32-bit platforms on overflows (GH6915)
  • Moved Panel.shift to NDFrame.slice_shift and fixed to respect multiple dtypes. (GH6959)
  • Bug in enabling subplots=True in DataFrame.plot only has single column raises TypeError, and Series.plot raises AttributeError (GH6951)
  • Bug in DataFrame.plot draws unnecessary axes when enabling subplots and kind=scatter (GH6951)
  • Bug in read_csv from a filesystem with non-utf-8 encoding (GH6807)
  • Bug in iloc when setting / aligning (GH6766)
  • Bug causing UnicodeEncodeError when get_dummies called with unicode values and a prefix (GH6885)
  • Bug in timeseries-with-frequency plot cursor display (GH5453)
  • Bug surfaced in groupby.plot when using a Float64Index (GH7025)
  • Stopped tests from failing if options data isn’t able to be downloaded from Yahoo (GH7034)
  • Bug in parallel_coordinates and radviz where reordering of class column caused possible color/class mismatch (GH6956)
  • Bug in radviz and andrews_curves where multiple values of ‘color’ were being passed to plotting method (GH6956)
  • Bug in Float64Index.isin() where containing nan s would make indices claim that they contained all the things (GH7066).
  • Bug in DataFrame.boxplot where it failed to use the axis passed as the ax argument (GH3578)
  • Bug in the XlsxWriter and XlwtWriter implementations that resulted in datetime columns being formatted without the time (GH7075) were being passed to plotting method
  • read_fwf() treats None in colspec like regular python slices. It now reads from the beginning or until the end of the line when colspec contains a None (previously raised a TypeError)
  • Bug in cache coherence with chained indexing and slicing; add _is_view property to NDFrame to correctly predict views; mark is_copy on xs only if its an actual copy (and not a view) (GH7084)
  • Bug in DatetimeIndex creation from string ndarray with dayfirst=True (GH5917)
  • Bug in MultiIndex.from_arrays created from DatetimeIndex doesn’t preserve freq and tz (GH7090)
  • Bug in unstack raises ValueError when MultiIndex contains PeriodIndex (GH4342)
  • Bug in boxplot and hist draws unnecessary axes (GH6769)
  • Regression in groupby.nth() for out-of-bounds indexers (GH6621)
  • Bug in quantile with datetime values (GH6965)
  • Bug in Dataframe.set_index, reindex and pivot don’t preserve DatetimeIndex and PeriodIndex attributes (GH3950, GH5878, GH6631)
  • Bug in MultiIndex.get_level_values doesn’t preserve DatetimeIndex and PeriodIndex attributes (GH7092)
  • Bug in Groupby doesn’t preserve tz (GH3950)
  • Bug in PeriodIndex partial string slicing (GH6716)
  • Bug in the HTML repr of a truncated Series or DataFrame not showing the class name with the large_repr set to ‘info’ (GH7105)
  • Bug in DatetimeIndex specifying freq raises ValueError when passed value is too short (GH7098)
  • Fixed a bug with the info repr not honoring the display.max_info_columns setting (GH6939)
  • Bug PeriodIndex string slicing with out of bounds values (GH5407)
  • Fixed a memory error in the hashtable implementation/factorizer on resizing of large tables (GH7157)
  • Bug in isnull when applied to 0-dimensional object arrays (GH7176)
  • Bug in query/eval where global constants were not looked up correctly (GH7178)
  • Bug in recognizing out-of-bounds positional list indexers with iloc and a multi-axis tuple indexer (GH7189)
  • Bug in setitem with a single value, multi-index and integer indices (GH7190, GH7218)
  • Bug in expressions evaluation with reversed ops, showing in series-dataframe ops (GH7198, GH7192)
  • Bug in multi-axis indexing with > 2 ndim and a multi-index (GH7199)
  • Fix a bug where invalid eval/query operations would blow the stack (GH5198)

v0.13.1 (February 3, 2014)

This is a minor release from 0.13.0 and includes a small number of API changes, several new features, enhancements, and performance improvements along with a large number of bug fixes. We recommend that all users upgrade to this version.

Highlights include:

  • Added infer_datetime_format keyword to read_csv/to_datetime to allow speedups for homogeneously formatted datetimes.
  • Will intelligently limit display precision for datetime/timedelta formats.
  • Enhanced Panel apply() method.
  • Suggested tutorials in new Tutorials section.
  • Our pandas ecosystem is growing, We now feature related projects in a new Pandas Ecosystem section.
  • Much work has been taking place on improving the docs, and a new Contributing section has been added.
  • Even though it may only be of interest to devs, we <3 our new CI status page: ScatterCI.


0.13.1 fixes a bug that was caused by a combination of having numpy < 1.8, and doing chained assignment on a string-like array. Please review the docs, chained indexing can have unexpected results and should generally be avoided.

This would previously segfault:

In [1]: df = DataFrame(dict(A = np.array(['foo','bar','bah','foo','bar'])))

In [2]: df['A'].iloc[0] = np.nan

In [3]: df
0  NaN
1  bar
2  bah
3  foo
4  bar

The recommended way to do this type of assignment is:

In [4]: df = DataFrame(dict(A = np.array(['foo','bar','bah','foo','bar'])))

In [5]: df.ix[0,'A'] = np.nan

In [6]: df
0  NaN
1  bar
2  bah
3  foo
4  bar

Output Formatting Enhancements

  • view now display dtype info per column (GH5682)

  • now honors the option max_info_rows, to disable null counts for large frames (GH5974)

    In [7]: max_info_rows = pd.get_option('max_info_rows')
    In [8]: df = DataFrame(dict(A = np.random.randn(10),
       ...:                     B = np.random.randn(10),
       ...:                     C = date_range('20130101',periods=10)))
    In [9]: df.iloc[3:6,[0,2]] = np.nan
    # set to not display the null counts
    In [10]: pd.set_option('max_info_rows',0)
    In [11]:
    <class 'pandas.core.frame.DataFrame'>
    Int64Index: 10 entries, 0 to 9
    Data columns (total 3 columns):
    A    float64
    B    float64
    C    datetime64[ns]
    dtypes: datetime64[ns](1), float64(2)
    memory usage: 320.0 bytes
    # this is the default (same as in 0.13.0)
    In [12]: pd.set_option('max_info_rows',max_info_rows)
    In [13]:
    <class 'pandas.core.frame.DataFrame'>
    Int64Index: 10 entries, 0 to 9
    Data columns (total 3 columns):
    A    7 non-null float64
    B    10 non-null float64
    C    7 non-null datetime64[ns]
    dtypes: datetime64[ns](1), float64(2)
    memory usage: 320.0 bytes
  • Add show_dimensions display option for the new DataFrame repr to control whether the dimensions print.

    In [14]: df = DataFrame([[1, 2], [3, 4]])
    In [15]: pd.set_option('show_dimensions', False)
    In [16]: df
       0  1
    0  1  2
    1  3  4
    In [17]: pd.set_option('show_dimensions', True)
    In [18]: df
       0  1
    0  1  2
    1  3  4
    [2 rows x 2 columns]
  • The ArrayFormatter for datetime and timedelta64 now intelligently limit precision based on the values in the array (GH3401)

    Previously output might look like:

      age                 today               diff
    0 2001-01-01 00:00:00 2013-04-19 00:00:00 4491 days, 00:00:00
    1 2004-06-01 00:00:00 2013-04-19 00:00:00 3244 days, 00:00:00

    Now the output looks like:

    In [19]: df = DataFrame([ Timestamp('20010101'),
       ....:                  Timestamp('20040601') ], columns=['age'])
    In [20]: df['today'] = Timestamp('20130419')
    In [21]: df['diff'] = df['today']-df['age']
    In [22]: df
             age      today      diff
    0 2001-01-01 2013-04-19 4491 days
    1 2004-06-01 2013-04-19 3244 days
    [2 rows x 3 columns]

API changes

  • Add -NaN and -nan to the default set of NA values (GH5952). See NA Values.

  • Added Series.str.get_dummies vectorized string method (GH6021), to extract dummy/indicator variables for separated string columns:

    In [23]: s = Series(['a', 'a|b', np.nan, 'a|c'])
    In [24]: s.str.get_dummies(sep='|')
       a  b  c
    0  1  0  0
    1  1  1  0
    2  0  0  0
    3  1  0  1
    [4 rows x 3 columns]
  • Added the NDFrame.equals() method to compare if two NDFrames are equal have equal axes, dtypes, and values. Added the array_equivalent function to compare if two ndarrays are equal. NaNs in identical locations are treated as equal. (GH5283) See also the docs for a motivating example.

    In [25]: df = DataFrame({'col':['foo', 0, np.nan]})
    In [26]: df2 = DataFrame({'col':[np.nan, 0, 'foo']}, index=[2,1,0])
    In [27]: df.equals(df2)
    Out[27]: False
    In [28]: df.equals(df2.sort())
    Out[28]: True
    In [29]: import pandas.core.common as com
    In [30]: com.array_equivalent(np.array([0, np.nan]), np.array([0, np.nan]))
    Out[30]: True
    In [31]: np.array_equal(np.array([0, np.nan]), np.array([0, np.nan]))
    Out[31]: False
  • DataFrame.apply will use the reduce argument to determine whether a Series or a DataFrame should be returned when the DataFrame is empty (GH6007).

    Previously, calling DataFrame.apply an empty DataFrame would return either a DataFrame if there were no columns, or the function being applied would be called with an empty Series to guess whether a Series or DataFrame should be returned:

    In [32]: def applied_func(col):
       ....:    print("Apply function being called with: ", col)
       ....:    return col.sum()
    In [33]: empty = DataFrame(columns=['a', 'b'])
    In [34]: empty.apply(applied_func)
    ('Apply function being called with: ', Series([], dtype: float64))
    a   NaN
    b   NaN
    dtype: float64

    Now, when apply is called on an empty DataFrame: if the reduce argument is True a Series will returned, if it is False a DataFrame will be returned, and if it is None (the default) the function being applied will be called with an empty series to try and guess the return type.

    In [35]: empty.apply(applied_func, reduce=True)
    a   NaN
    b   NaN
    dtype: float64
    In [36]: empty.apply(applied_func, reduce=False)
    Empty DataFrame
    Columns: [a, b]
    Index: []
    [0 rows x 2 columns]