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# Version 0.11.0 (April 22, 2013)

This is a major release from 0.10.1 and includes many new features and enhancements along with a large number of bug fixes. The methods of Selecting Data have had quite a number of additions, and Dtype support is now full-fledged. There are also a number of important API changes that long-time pandas users should pay close attention to.

There is a new section in the documentation, 10 Minutes to Pandas, primarily geared to new users.

There is a new section in the documentation, Cookbook, a collection of useful recipes in pandas (and that we want contributions!).

There are several libraries that are now Recommended Dependencies

## Selection choices

Starting in 0.11.0, object selection has had a number of user-requested additions in order to support more explicit location based indexing. pandas now supports three types of multi-axis indexing.

- `.loc` is strictly label based, will raise `KeyError` when the items are not found, allowed inputs are:

  - A single label, e.g. `5` or `'a'`, (note that `5` is interpreted as a label of the index. This use is not an integer position along the index)

  - A list or array of labels `['a', 'b', 'c']`

  - A slice object with labels `'a':'f'`, (note that contrary to usual python slices, both the start and the stop are included!)

  - A boolean array

  See more at Selection by Label

- `.iloc` is strictly integer position based (from `0` to `length-1` of the axis), will raise `IndexError` when the requested indices are out of bounds. Allowed inputs are:

  - An integer e.g. `5`

  - A list or array of integers `[4, 3, 0]`

  - A slice object with ints `1:7`

  - A boolean array

  See more at Selection by Position

- `.ix` supports mixed integer and label based access. It is primarily label based, but will fallback to integer positional access. `.ix` is the most general and will support any of the inputs to `.loc` and `.iloc`, as well as support for floating point label schemes. `.ix` is especially useful when dealing with mixed positional and label based hierarchical indexes.

  As using integer slices with `.ix` have different behavior depending on whether the slice is interpreted as position based or label based, it’s usually better to be explicit and use `.iloc` or `.loc`.

  See more at Advanced Indexing and Advanced Hierarchical.

## Selection deprecations

Starting in version 0.11.0, these methods may be deprecated in future versions.

- `irow`

- `icol`

- `iget_value`

See the section Selection by Position for substitutes.

## Dtypes

Numeric dtypes will propagate and can coexist in DataFrames. If a dtype is passed (either directly via the `dtype` keyword, a passed `ndarray`, or a passed `Series`, then it will be preserved in DataFrame operations. Furthermore, different numeric dtypes will NOT be combined. The following example will give you a taste.

    In [1]: df1 = pd.DataFrame(np.random.randn(8, 1), columns=['A'], dtype='float32')

    In [2]: df1
    Out[2]:
              A
    0  0.469112
    1 -0.282863
    2 -1.509058
    3 -1.135632
    4  1.212112
    5 -0.173215
    6  0.119209
    7 -1.044236

    In [3]: df1.dtypes
    Out[3]:
    A    float32
    dtype: object

    In [4]: df2 = pd.DataFrame({'A': pd.Series(np.random.randn(8), dtype='float16'),
       ...:                     'B': pd.Series(np.random.randn(8)),
       ...:                     'C': pd.Series(range(8), dtype='uint8')})
       ...:

    In [5]: df2
    Out[5]:
              A         B  C
    0 -0.861816 -0.424972  0
    1 -2.105469  0.567020  1
    2 -0.494873  0.276232  2
    3  1.072266 -1.087401  3
    4  0.721680 -0.673690  4
    5 -0.706543  0.113648  5
    6 -1.040039 -1.478427  6
    7  0.271973  0.524988  7

    In [6]: df2.dtypes
    Out[6]:
    A    float16
    B    float64
    C      uint8
    dtype: object

    # here you get some upcasting
    In [7]: df3 = df1.reindex_like(df2).fillna(value=0.0) + df2

    In [8]: df3
    Out[8]:
              A         B    C
    0 -0.392704 -0.424972  0.0
    1 -2.388332  0.567020  1.0
    2 -2.003932  0.276232  2.0
    3 -0.063367 -1.087401  3.0
    4  1.933792 -0.673690  4.0
    5 -0.879758  0.113648  5.0
    6 -0.920830 -1.478427  6.0
    7 -0.772263  0.524988  7.0

    In [9]: df3.dtypes
    Out[9]:
    A    float32
    B    float64
    C    float64
    dtype: object

## Dtype conversion

This is lower-common-denominator upcasting, meaning you get the dtype which can accommodate all of the types

    In [10]: df3.values.dtype
    Out[10]: dtype('float64')

Conversion

    In [11]: df3.astype('float32').dtypes
    Out[11]:
    A    float32
    B    float32
    C    float32
    dtype: object

Mixed conversion

    In [12]: df3['D'] = '1.'

    In [13]: df3['E'] = '1'

    In [14]: df3.convert_objects(convert_numeric=True).dtypes
    Out[14]:
    A    float32
    B    float64
    C    float64
    D    float64
    E      int64
    dtype: object

    # same, but specific dtype conversion
    In [15]: df3['D'] = df3['D'].astype('float16')

    In [16]: df3['E'] = df3['E'].astype('int32')

    In [17]: df3.dtypes
    Out[17]:
    A    float32
    B    float64
    C    float64
    D    float16
    E      int32
    dtype: object

Forcing date coercion (and setting `NaT` when not datelike)

    In [18]: import datetime

    In [19]: s = pd.Series([datetime.datetime(2001, 1, 1, 0, 0), 'foo', 1.0, 1,
       ....:                pd.Timestamp('20010104'), '20010105'], dtype='O')
       ....:

    In [20]: s.convert_objects(convert_dates='coerce')
    Out[20]:
    0   2001-01-01
    1          NaT
    2          NaT
    3          NaT
    4   2001-01-04
    5   2001-01-05
    dtype: datetime64[ns]

## Dtype gotchas

Platform gotchas

Starting in 0.11.0, construction of DataFrame/Series will use default dtypes of `int64` and `float64`, regardless of platform. This is not an apparent change from earlier versions of pandas. If you specify dtypes, they WILL be respected, however (GH 2837)

The following will all result in `int64` dtypes

    In [21]: pd.DataFrame([1, 2], columns=['a']).dtypes
    Out[21]:
    a    int64
    dtype: object

    In [22]: pd.DataFrame({'a': [1, 2]}).dtypes
    Out[22]:
    a    int64
    dtype: object

    In [23]: pd.DataFrame({'a': 1}, index=range(2)).dtypes
    Out[23]:
    a    int64
    dtype: object

Keep in mind that `DataFrame(np.array([1,2]))` WILL result in `int32` on 32-bit platforms!

Upcasting gotchas

Performing indexing operations on integer type data can easily upcast the data. The dtype of the input data will be preserved in cases where `nans` are not introduced.

    In [24]: dfi = df3.astype('int32')

    In [25]: dfi['D'] = dfi['D'].astype('int64')

    In [26]: dfi
    Out[26]:
      A  B  C  D  E
    0  0  0  0  1  1
    1 -2  0  1  1  1
    2 -2  0  2  1  1
    3  0 -1  3  1  1
    4  1  0  4  1  1
    5  0  0  5  1  1
    6  0 -1  6  1  1
    7  0  0  7  1  1

    In [27]: dfi.dtypes
    Out[27]:
    A    int32
    B    int32
    C    int32
    D    int64
    E    int32
    dtype: object

    In [28]: casted = dfi[dfi > 0]

    In [29]: casted
    Out[29]:
        A   B    C  D  E
    0  NaN NaN  NaN  1  1
    1  NaN NaN  1.0  1  1
    2  NaN NaN  2.0  1  1
    3  NaN NaN  3.0  1  1
    4  1.0 NaN  4.0  1  1
    5  NaN NaN  5.0  1  1
    6  NaN NaN  6.0  1  1
    7  NaN NaN  7.0  1  1

    In [30]: casted.dtypes
    Out[30]:
    A    float64
    B    float64
    C    float64
    D      int64
    E      int32
    dtype: object

While float dtypes are unchanged.

    In [31]: df4 = df3.copy()

    In [32]: df4['A'] = df4['A'].astype('float32')

    In [33]: df4.dtypes
    Out[33]:
    A    float32
    B    float64
    C    float64
    D    float16
    E      int32
    dtype: object

    In [34]: casted = df4[df4 > 0]

    In [35]: casted
    Out[35]:
              A         B    C    D  E
    0       NaN       NaN  NaN  1.0  1
    1       NaN  0.567020  1.0  1.0  1
    2       NaN  0.276232  2.0  1.0  1
    3       NaN       NaN  3.0  1.0  1
    4  1.933792       NaN  4.0  1.0  1
    5       NaN  0.113648  5.0  1.0  1
    6       NaN       NaN  6.0  1.0  1
    7       NaN  0.524988  7.0  1.0  1

    In [36]: casted.dtypes
    Out[36]:
    A    float32
    B    float64
    C    float64
    D    float16
    E      int32
    dtype: object

## Datetimes conversion

Datetime64[ns] columns in a DataFrame (or a Series) allow the use of `np.nan` to indicate a nan value, in addition to the traditional `NaT`, or not-a-time. This allows convenient nan setting in a generic way. Furthermore `datetime64[ns]` columns are created by default, when passed datetimelike objects (this change was introduced in 0.10.1) (GH 2809, GH 2810)

    In [12]: df = pd.DataFrame(np.random.randn(6, 2), pd.date_range('20010102', periods=6),
       ....:                   columns=['A', ' B'])
       ....:

    In [13]: df['timestamp'] = pd.Timestamp('20010103')

    In [14]: df
    Out[14]:
                       A         B  timestamp
    2001-01-02  0.404705  0.577046 2001-01-03
    2001-01-03 -1.715002 -1.039268 2001-01-03
    2001-01-04 -0.370647 -1.157892 2001-01-03
    2001-01-05 -1.344312  0.844885 2001-01-03
    2001-01-06  1.075770 -0.109050 2001-01-03
    2001-01-07  1.643563 -1.469388 2001-01-03

    # datetime64[ns] out of the box
    In [15]: df.dtypes.value_counts()
    Out[15]:
    float64          2
    datetime64[s]    1
    Name: count, dtype: int64

    # use the traditional nan, which is mapped to NaT internally
    In [16]: df.loc[df.index[2:4], ['A', 'timestamp']] = np.nan

    In [17]: df
    Out[17]:
                       A         B  timestamp
    2001-01-02  0.404705  0.577046 2001-01-03
    2001-01-03 -1.715002 -1.039268 2001-01-03
    2001-01-04       NaN -1.157892        NaT
    2001-01-05       NaN  0.844885        NaT
    2001-01-06  1.075770 -0.109050 2001-01-03
    2001-01-07  1.643563 -1.469388 2001-01-03

Astype conversion on `datetime64[ns]` to `object`, implicitly converts `NaT` to `np.nan`

    In [18]: import datetime

    In [19]: s = pd.Series([datetime.datetime(2001, 1, 2, 0, 0) for i in range(3)])

    In [20]: s.dtype
    Out[20]: dtype('<M8[ns]')

    In [21]: s[1] = np.nan

    In [22]: s
    Out[22]:
    0   2001-01-02
    1          NaT
    2   2001-01-02
    dtype: datetime64[ns]

    In [23]: s.dtype
    Out[23]: dtype('<M8[ns]')

    In [24]: s = s.astype('O')

    In [25]: s
    Out[25]:
    0    2001-01-02 00:00:00
    1                    NaT
    2    2001-01-02 00:00:00
    dtype: object

    In [26]: s.dtype
    Out[26]: dtype('O')

## API changes

> - Added to_series() method to indices, to facilitate the creation of indexers (GH 3275)

> - `HDFStore`

>   - added the method `select_column` to select a single column from a table as a Series.

>   - deprecated the `unique` method, can be replicated by `select_column(key,column).unique()`

>   - `min_itemsize` parameter to `append` will now automatically create data_columns for passed keys

## Enhancements

> - Improved performance of df.to_csv() by up to 10x in some cases. (GH 3059)

> - Numexpr is now a Recommended Dependencies, to accelerate certain types of numerical and boolean operations

> - Bottleneck is now a Recommended Dependencies, to accelerate certain types of `nan` operations

> - `HDFStore`

>   - support `read_hdf/to_hdf` API similar to `read_csv/to_csv`

>         In [27]: df = pd.DataFrame({'A': range(5), 'B': range(5)})

>         In [28]: df.to_hdf('store.h5', key='table', append=True)

>         In [29]: pd.read_hdf('store.h5', 'table', where=['index > 2'])
>         Out[29]:
>            A  B
>         3  3  3
>         4  4  4

>   - provide dotted attribute access to `get` from stores, e.g. `store.df == store['df']`

>   - new keywords `iterator=boolean`, and `chunksize=number_in_a_chunk` are provided to support iteration on `select` and `select_as_multiple` (GH 3076)

> - You can now select timestamps from an unordered timeseries similarly to an ordered timeseries (GH 2437)

> - You can now select with a string from a DataFrame with a datelike index, in a similar way to a Series (GH 3070)

>       In [30]: idx = pd.date_range("2001-10-1", periods=5, freq='M')

>       In [31]: ts = pd.Series(np.random.rand(len(idx)), index=idx)

>       In [32]: ts['2001']
>       Out[32]:
>       2001-10-31    0.117967
>       2001-11-30    0.702184
>       2001-12-31    0.414034
>       Freq: M, dtype: float64

>       In [33]: df = pd.DataFrame({'A': ts})

>       In [34]: df['2001']
>       Out[34]:
>                          A
>       2001-10-31  0.117967
>       2001-11-30  0.702184
>       2001-12-31  0.414034

> - `Squeeze` to possibly remove length 1 dimensions from an object.

>       >>> p = pd.Panel(np.random.randn(3, 4, 4), items=['ItemA', 'ItemB', 'ItemC'],
>       ...              major_axis=pd.date_range('20010102', periods=4),
>       ...              minor_axis=['A', 'B', 'C', 'D'])
>       >>> p
>       <class 'pandas.core.panel.Panel'>
>       Dimensions: 3 (items) x 4 (major_axis) x 4 (minor_axis)
>       Items axis: ItemA to ItemC
>       Major_axis axis: 2001-01-02 00:00:00 to 2001-01-05 00:00:00
>       Minor_axis axis: A to D

>       >>> p.reindex(items=['ItemA']).squeeze()
>                          A         B         C         D
>       2001-01-02  0.926089 -2.026458  0.501277 -0.204683
>       2001-01-03 -0.076524  1.081161  1.141361  0.479243
>       2001-01-04  0.641817 -0.185352  1.824568  0.809152
>       2001-01-05  0.575237  0.669934  1.398014 -0.399338

>       >>> p.reindex(items=['ItemA'], minor=['B']).squeeze()
>       2001-01-02   -2.026458
>       2001-01-03    1.081161
>       2001-01-04   -0.185352
>       2001-01-05    0.669934
>       Freq: D, Name: B, dtype: float64

> - In `pd.io.data.Options`,

>   - Fix bug when trying to fetch data for the current month when already past expiry.

>   - Now using lxml to scrape html instead of BeautifulSoup (lxml was faster).

>   - New instance variables for calls and puts are automatically created when a method that creates them is called. This works for current month where the instance variables are simply `calls` and `puts`. Also works for future expiry months and save the instance variable as `callsMMYY` or `putsMMYY`, where `MMYY` are, respectively, the month and year of the option’s expiry.

>   - `Options.get_near_stock_price` now allows the user to specify the month for which to get relevant options data.

>   - `Options.get_forward_data` now has optional kwargs `near` and `above_below`. This allows the user to specify if they would like to only return forward looking data for options near the current stock price. This just obtains the data from Options.get_near_stock_price instead of Options.get_xxx_data() (GH 2758).

> - Cursor coordinate information is now displayed in time-series plots.

> - added option `display.max_seq_items` to control the number of elements printed per sequence pprinting it. (GH 2979)

> - added option `display.chop_threshold` to control display of small numerical values. (GH 2739)

> - added option `display.max_info_rows` to prevent verbose_info from being calculated for frames above 1M rows (configurable). (GH 2807, GH 2918)

> - value_counts() now accepts a “normalize” argument, for normalized histograms. (GH 2710).

> - DataFrame.from_records now accepts not only dicts but any instance of the collections.Mapping ABC.

> - added option `display.mpl_style` providing a sleeker visual style for plots. Based on https://gist.github.com/huyng/816622 (GH 3075).

> - Treat boolean values as integers (values 1 and 0) for numeric operations. (GH 2641)

> - to_html() now accepts an optional “escape” argument to control reserved HTML character escaping (enabled by default) and escapes `&`, in addition to `<` and `>`. (GH 2919)

See the full release notes or issue tracker on GitHub for a complete list.

## Contributors

A total of 50 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.

- Adam Greenhall +

- Alvaro Tejero-Cantero +

- Andy Hayden

- Brad Buran +

- Chang She

- Chapman Siu +

- Chris Withers +

- Christian Geier +

- Christopher Whelan

- Damien Garaud

- Dan Birken

- Dan Davison +

- Dieter Vandenbussche

- Dražen Lučanin +

- Dražen Lučanin +

- Garrett Drapala

- Illia Polosukhin +

- James Casbon +

- Jeff Reback

- Jeremy Wagner +

- Jonathan Chambers +

- K.-Michael Aye

- Karmel Allison +

- Loïc Estève +

- Nicholaus E. Halecky +

- Peter Prettenhofer +

- Phillip Cloud +

- Robert Gieseke +

- Skipper Seabold

- Spencer Lyon

- Stephen Lin +

- Thierry Moisan +

- Thomas Kluyver

- Tim Akinbo +

- Vytautas Jancauskas

- Vytautas Jančauskas +

- Wes McKinney

- Will Furnass +

- Wouter Overmeire

- anomrake +

- davidjameshumphreys +

- dengemann +

- dieterv77 +

- jreback

- lexual +

- stephenwlin +

- thauck +

- vytas +

- waitingkuo +

- y-p