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# What’s new in 2.2.1 (February 22, 2024)

These are the changes in pandas 2.2.1. See Release notes for a full changelog including other versions of pandas.

## Enhancements

- Added `pyarrow` pip extra so users can install pandas and pyarrow with pip with `pip install pandas[pyarrow]` (GH 54466)

## Fixed regressions

- Fixed memory leak in `read_csv()` (GH 57039)

- Fixed performance regression in `Series.combine_first()` (GH 55845)

- Fixed regression causing overflow for near-minimum timestamps (GH 57150)

- Fixed regression in `concat()` changing long-standing behavior that always sorted the non-concatenation axis when the axis was a `DatetimeIndex` (GH 57006)

- Fixed regression in `merge_ordered()` raising `TypeError` for `fill_method="ffill"` and `how="left"` (GH 57010)

- Fixed regression in `pandas.testing.assert_series_equal()` defaulting to `check_exact=True` when checking the `Index` (GH 57067)

- Fixed regression in `read_json()` where an `Index` would be returned instead of a `RangeIndex` (GH 57429)

- Fixed regression in `wide_to_long()` raising an `AttributeError` for string columns (GH 57066)

- Fixed regression in `DataFrameGroupBy.idxmin()`, `DataFrameGroupBy.idxmax()`, `SeriesGroupBy.idxmin()`, `SeriesGroupBy.idxmax()` ignoring the `skipna` argument (GH 57040)

- Fixed regression in `DataFrameGroupBy.idxmin()`, `DataFrameGroupBy.idxmax()`, `SeriesGroupBy.idxmin()`, `SeriesGroupBy.idxmax()` where values containing the minimum or maximum value for the dtype could produce incorrect results (GH 57040)

- Fixed regression in `CategoricalIndex.difference()` raising `KeyError` when other contains null values other than NaN (GH 57318)

- Fixed regression in `DataFrame.groupby()` raising `ValueError` when grouping by a `Series` in some cases (GH 57276)

- Fixed regression in `DataFrame.loc()` raising `IndexError` for non-unique, masked dtype indexes where result has more than 10,000 rows (GH 57027)

- Fixed regression in `DataFrame.loc()` which was unnecessarily throwing “incompatible dtype warning” when expanding with partial row indexer and multiple columns (see PDEP6) (GH 56503)

- Fixed regression in `DataFrame.map()` with `na_action="ignore"` not being respected for NumPy nullable and `ArrowDtypes` (GH 57316)

- Fixed regression in `DataFrame.merge()` raising `ValueError` for certain types of 3rd-party extension arrays (GH 57316)

- Fixed regression in `DataFrame.query()` with all `NaT` column with object dtype (GH 57068)

- Fixed regression in `DataFrame.shift()` raising `AssertionError` for `axis=1` and empty `DataFrame` (GH 57301)

- Fixed regression in `DataFrame.sort_index()` not producing a stable sort for a index with duplicates (GH 57151)

- Fixed regression in `DataFrame.to_dict()` with `orient='list'` and datetime or timedelta types returning integers (GH 54824)

- Fixed regression in `DataFrame.to_json()` converting nullable integers to floats (GH 57224)

- Fixed regression in `DataFrame.to_sql()` when `method="multi"` is passed and the dialect type is not Oracle (GH 57310)

- Fixed regression in `DataFrame.transpose()` with nullable extension dtypes not having F-contiguous data potentially causing exceptions when used (GH 57315)

- Fixed regression in `DataFrame.update()` emitting incorrect warnings about downcasting (GH 57124)

- Fixed regression in `DataFrameGroupBy.idxmin()`, `DataFrameGroupBy.idxmax()`, `SeriesGroupBy.idxmin()`, `SeriesGroupBy.idxmax()` ignoring the `skipna` argument (GH 57040)

- Fixed regression in `DataFrameGroupBy.idxmin()`, `DataFrameGroupBy.idxmax()`, `SeriesGroupBy.idxmin()`, `SeriesGroupBy.idxmax()` where values containing the minimum or maximum value for the dtype could produce incorrect results (GH 57040)

- Fixed regression in `ExtensionArray.to_numpy()` raising for non-numeric masked dtypes (GH 56991)

- Fixed regression in `Index.join()` raising `TypeError` when joining an empty index to a non-empty index containing mixed dtype values (GH 57048)

- Fixed regression in `Series.astype()` introducing decimals when converting from integer with missing values to string dtype (GH 57418)

- Fixed regression in `Series.pct_change()` raising a `ValueError` for an empty `Series` (GH 57056)

- Fixed regression in `Series.to_numpy()` when dtype is given as float and the data contains NaNs (GH 57121)

- Fixed regression in addition or subtraction of `DateOffset` objects with millisecond components to `datetime64` `Index`, `Series`, or `DataFrame` (GH 57529)

## Bug fixes

- Fixed bug in `pandas.api.interchange.from_dataframe()` which was raising for Nullable integers (GH 55069)

- Fixed bug in `pandas.api.interchange.from_dataframe()` which was raising for empty inputs (GH 56700)

- Fixed bug in `pandas.api.interchange.from_dataframe()` which wasn’t converting columns names to strings (GH 55069)

- Fixed bug in `DataFrame.__getitem__()` for empty `DataFrame` with Copy-on-Write enabled (GH 57130)

- Fixed bug in `PeriodIndex.asfreq()` which was silently converting frequencies which are not supported as period frequencies instead of raising an error (GH 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 `DataFrameGroupBy.first()`, `DataFrameGroupBy.last()`, `SeriesGroupBy.first()`, and `SeriesGroupBy.last()`; achieving `skipna=False` used to be available via `DataFrameGroupBy.nth()`, but the behavior was changed in pandas 2.0.0 (GH 57019)

- Added the argument `skipna` to `Resampler.first()`, `Resampler.last()` (GH 57019)

## Contributors

A total of 14 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.

- Albert Villanova del Moral

- Luke Manley

- Lumberbot (aka Jack)

- Marco Edward Gorelli

- Matthew Roeschke

- Natalia Mokeeva

- Pandas Development Team

- Patrick Hoefler

- Richard Shadrach

- Robert Schmidtke +

- Samuel Chai +

- Thomas Li

- William Ayd

- dependabot[bot]