v2.2.1.rst

What's new in 2.2.1 (February XX, 2024)

These are the changes in pandas 2.2.1. See :ref:`release` for a full changelog including other versions of pandas.

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Fixed regressions

• Fixed memory leak in :func:`read_csv` (:issue:`57039`)
• Fixed performance regression in :meth:`Series.combine_first` (:issue:`55845`)
• Fixed regression in :func:`concat` changing long-standing behavior that always sorted the non-concatenation axis when the axis was a :class:`DatetimeIndex` (:issue:`57006`)
• Fixed regression in :func:`merge_ordered` raising TypeError for fill_method="ffill" and how="left" (:issue:`57010`)
• Fixed regression in :func:`pandas.testing.assert_series_equal` defaulting to check_exact=True when checking the :class:`Index` (:issue:`57067`)
• Fixed regression in :func:`wide_to_long` raising an AttributeError for string columns (:issue:`57066`)
• Fixed regression in :meth:`.DataFrameGroupBy.idxmin`, :meth:`.DataFrameGroupBy.idxmax`, :meth:`.SeriesGroupBy.idxmin`, :meth:`.SeriesGroupBy.idxmax` ignoring the skipna argument (:issue:`57040`)
• Fixed regression in :meth:`.DataFrameGroupBy.idxmin`, :meth:`.DataFrameGroupBy.idxmax`, :meth:`.SeriesGroupBy.idxmin`, :meth:`.SeriesGroupBy.idxmax` where values containing the minimum or maximum value for the dtype could produce incorrect results (:issue:`57040`)
• Fixed regression in :meth:`CategoricalIndex.difference` raising KeyError when other contains null values other than NaN (:issue:`57318`)
• Fixed regression in :meth:`DataFrame.groupby` raising ValueError when grouping by a :class:`Series` in some cases (:issue:`57276`)
• Fixed regression in :meth:`DataFrame.loc` raising IndexError for non-unique, masked dtype indexes where result has more than 10,000 rows (:issue:`57027`)
• Fixed regression in :meth:`DataFrame.loc` which was unnecessarily throwing "incompatible dtype warning" when expanding with partial row indexer and multiple columns (see PDEP6) (:issue:`56503`)
• Fixed regression in :meth:`DataFrame.map` with na_action="ignore" not being respected for NumPy nullable and :class:`ArrowDtypes` (:issue:`57316`)
• Fixed regression in :meth:`DataFrame.merge` raising ValueError for certain types of 3rd-party extension arrays (:issue:`57316`)
• Fixed regression in :meth:`DataFrame.shift` raising AssertionError for axis=1 and empty :class:`DataFrame` (:issue:`57301`)
• Fixed regression in :meth:`DataFrame.sort_index` not producing a stable sort for a index with duplicates (:issue:`57151`)
• Fixed regression in :meth:`DataFrame.to_dict` with orient='list' and datetime or timedelta types returning integers (:issue:`54824`)
• Fixed regression in :meth:`DataFrame.to_json` converting nullable integers to floats (:issue:`57224`)
• Fixed regression in :meth:`DataFrame.to_sql` when method="multi" is passed and the dialect type is not Oracle (:issue:`57310`)
• Fixed regression in :meth:`DataFrame.transpose` with nullable extension dtypes not having F-contiguous data potentially causing exceptions when used (:issue:`57315`)
• Fixed regression in :meth:`DataFrameGroupBy.idxmin`, :meth:`DataFrameGroupBy.idxmax`, :meth:`SeriesGroupBy.idxmin`, :meth:`SeriesGroupBy.idxmax` ignoring the skipna argument (:issue:`57040`)
• Fixed regression in :meth:`DataFrameGroupBy.idxmin`, :meth:`DataFrameGroupBy.idxmax`, :meth:`SeriesGroupBy.idxmin`, :meth:`SeriesGroupBy.idxmax` where values containing the minimum or maximum value for the dtype could produce incorrect results (:issue:`57040`)
• Fixed regression in :meth:`ExtensionArray.to_numpy` raising for non-numeric masked dtypes (:issue:`56991`)
• Fixed regression in :meth:`Index.join` raising TypeError when joining an empty index to a non-empty index containing mixed dtype values (:issue:`57048`)
• Fixed regression in :meth:`Series.pct_change` raising a ValueError for an empty :class:`Series` (:issue:`57056`)
• Fixed regression in :meth:`Series.to_numpy` when dtype is given as float and the data contains NaNs (:issue:`57121`)

Bug fixes

• Fixed bug in :func:`pandas.api.interchange.from_dataframe` which was raising for Nullable integers (:issue:`55069`)
• Fixed bug in :func:`pandas.api.interchange.from_dataframe` which was raising for empty inputs (:issue:`56700`)
• Fixed bug in :func:`pandas.api.interchange.from_dataframe` which wasn't converting columns names to strings (:issue:`55069`)
• Fixed bug in :meth:`DataFrame.__getitem__` for empty :class:`DataFrame` with Copy-on-Write enabled (:issue:`57130`)
• Fixed bug in :meth:`PeriodIndex.asfreq` which was silently converting frequencies which are not supported as period frequencies instead of raising an error (:issue:`56945`)

Other

• Added the argument skipna to :meth:`DataFrameGroupBy.first`, :meth:`DataFrameGroupBy.last`, :meth:`SeriesGroupBy.first`, and :meth:`SeriesGroupBy.last`; achieving skipna=False used to be available via :meth:`DataFrameGroupBy.nth`, but the behavior was changed in pandas 2.0.0 (:issue:`57019`)
• Added the argument skipna to :meth:`Resampler.first`, :meth:`Resampler.last` (:issue:`57019`)

Contributors