What’s new in 1.0.1 (February 5, 2020)

These are the changes in pandas 1.0.1. See Release Notes for a full changelog including other versions of pandas.

Fixed regressions

  • Fixed regression in DataFrame setting values with a slice (e.g. df[-4:] = 1) indexing by label instead of position (GH31469)

  • Fixed regression when indexing a Series or DataFrame indexed by DatetimeIndex with a slice containg a datetime.date (GH31501)

  • Fixed regression in DataFrame.__setitem__ raising an AttributeError with a MultiIndex and a non-monotonic indexer (GH31449)

  • Fixed regression in Series multiplication when multiplying a numeric Series with >10000 elements with a timedelta-like scalar (GH31457)

  • Fixed regression in .groupby().agg() raising an AssertionError for some reductions like min on object-dtype columns (GH31522)

  • Fixed regression in .groupby() aggregations with categorical dtype using Cythonized reduction functions (e.g. first) (GH31450)

  • Fixed regression in GroupBy.apply() if called with a function which returned a non-pandas non-scalar object (e.g. a list or numpy array) (GH31441)

  • Fixed regression in DataFrame.groupby() whereby taking the minimum or maximum of a column with period dtype would raise a TypeError. (GH31471)

  • Fixed regression in DataFrame.groupby() with an empty DataFrame grouping by a level of a MultiIndex (GH31670).

  • Fixed regression in DataFrame.apply() with object dtype and non-reducing function (GH31505)

  • Fixed regression in to_datetime() when parsing non-nanosecond resolution datetimes (GH31491)

  • Fixed regression in to_csv() where specifying an na_rep might truncate the values written (GH31447)

  • Fixed regression in Categorical construction with numpy.str_ categories (GH31499)

  • Fixed regression in DataFrame.loc() and DataFrame.iloc() when selecting a row containing a single datetime64 or timedelta64 column (GH31649)

  • Fixed regression where setting pd.options.display.max_colwidth was not accepting negative integer. In addition, this behavior has been deprecated in favor of using None (GH31532)

  • Fixed regression in objTOJSON.c fix return-type warning (GH31463)

  • Fixed regression in qcut() when passed a nullable integer. (GH31389)

  • Fixed regression in assigning to a Series using a nullable integer dtype (GH31446)

  • Fixed performance regression when indexing a DataFrame or Series with a MultiIndex for the index using a list of labels (GH31648)

  • Fixed regression in read_csv() used in file like object RawIOBase is not recognize encoding option (GH31575)


  • Support for negative integer for pd.options.display.max_colwidth is deprecated in favor of using None (GH31532)

Bug fixes



  • Bug in dtypes being lost in DataFrame.__invert__ (~ operator) with mixed dtypes (GH31183) and for extension-array backed Series and DataFrame (GH23087)


  • Plotting tz-aware timeseries no longer gives UserWarning (GH31205)


  • Bug in Series.shift() with interval dtype raising a TypeError when shifting an interval array of integers or datetimes (GH34195)


A total of 7 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.

  • Guillaume Lemaitre

  • Jeff Reback

  • Joris Van den Bossche

  • Kaiqi Dong

  • MeeseeksMachine

  • Pandas Development Team

  • Tom Augspurger