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 memory leak in :func:`read_csv` (:issue:`57039`)
- Fixed performance regression in :meth:`Series.combine_first` (:issue:`55845`)
- Fixed regression in :func:`merge_ordered` raising
TypeErrorforfill_method="ffill"andhow="left"(:issue:`57010`) - Fixed regression in :func:`wide_to_long` raising an
AttributeErrorfor string columns (:issue:`57066`) - Fixed regression in :meth:`DataFrame.loc` raising
IndexErrorfor non-unique, masked dtype indexes where result has more than 10,000 rows (:issue:`57027`) - 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:`DataFrameGroupBy.idxmin`, :meth:`DataFrameGroupBy.idxmax`, :meth:`SeriesGroupBy.idxmin`, :meth:`SeriesGroupBy.idxmax` ignoring the
skipnaargument (: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:`Index.join` raising
TypeErrorwhen joining an empty index to a non-empty index containing mixed dtype values (:issue:`57048`) - Fixed regression in :meth:`Series.pct_change` raising a
ValueErrorfor an empty :class:`Series` (:issue:`57056`)
- 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`)
- Added the argument
skipnato :meth:`DataFrameGroupBy.first`, :meth:`DataFrameGroupBy.last`, :meth:`SeriesGroupBy.first`, and :meth:`SeriesGroupBy.last`; achievingskipna=Falseused to be available via :meth:`DataFrameGroupBy.nth`, but the behavior was changed in pandas 2.0.0 (:issue:`57019`) - Added the argument
skipnato :meth:`Resampler.first`, :meth:`Resampler.last` (:issue:`57019`)