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.query` with all NaT column with object dtype (:issue:`57068`)
• 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:`DataFrame.update` emitting incorrect warnings about downcasting (:issue:`57124`)
• 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.astype` introducing decimals when converting from integer with missing values to string dtype (:issue:`57418`)
• 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`)
• Fixed regression in addition or subtraction of :class:`DateOffset` objects with millisecond components to datetime64 :class:`Index`, :class:`Series`, or :class:`DataFrame` (:issue:`57529`)

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

Note

The DeprecationWarning that was raised when pandas was imported without PyArrow being installed has been removed. This decision was made because the warning was too noisy for too many users and a lot of feedback was collected about the decision to make PyArrow a required dependency. Pandas is currently considering the decision whether or not PyArrow should be added as a hard dependency in 3.0. Interested users can follow the discussion here.

• 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