What’s new in 2.1.1 (September 20, 2023)

These are the changes in pandas 2.1.1. See Release notes for a full changelog including other versions of pandas.

Fixed regressions

• Fixed regression in concat() when DataFrame ‘s have two different extension dtypes (GH 54848)

• Fixed regression in merge() when merging over a PyArrow string index (GH 54894)

• Fixed regression in read_csv() when usecols is given and dtypes is a dict for engine="python" (GH 54868)

• Fixed regression in read_csv() when delim_whitespace is True (GH 54918, GH 54931)

• Fixed regression in GroupBy.get_group() raising for axis=1 (GH 54858)

• Fixed regression in DataFrame.__setitem__() raising AssertionError when setting a Series with a partial MultiIndex (GH 54875)

• Fixed regression in DataFrame.filter() not respecting the order of elements for filter (GH 54980)

• Fixed regression in DataFrame.to_sql() not roundtripping datetime columns correctly for sqlite (GH 54877)

• Fixed regression in DataFrameGroupBy.agg() when aggregating a DataFrame with duplicate column names using a dictionary (GH 55006)

• Fixed regression in MultiIndex.append() raising when appending overlapping IntervalIndex levels (GH 54934)

• Fixed regression in Series.drop_duplicates() for PyArrow strings (GH 54904)

• Fixed regression in Series.interpolate() raising when fill_value was given (GH 54920)

• Fixed regression in Series.value_counts() raising for numeric data if bins was specified (GH 54857)

• Fixed regression in comparison operations for PyArrow backed columns not propagating exceptions correctly (GH 54944)

• Fixed regression when comparing a Series with datetime64 dtype with None (GH 54870)

Bug fixes

• Fixed bug for ArrowDtype raising NotImplementedError for fixed-size list (GH 55000)

• Fixed bug in DataFrame.stack() with future_stack=True and columns a non-MultiIndex consisting of tuples (GH 54948)

• Fixed bug in Series.dt.tz() with ArrowDtype where a string was returned instead of a tzinfo object (GH 55003)

• Fixed bug in Series.pct_change() and DataFrame.pct_change() showing unnecessary FutureWarning (GH 54981)

Other

• Reverted the deprecation that disallowed Series.apply() returning a DataFrame when the passed-in callable returns a Series object (GH 52116)

Contributors

For contributors, please see /usr/share/doc/contributors_list.txt or https://github.com/pandas-dev/pandas/graphs/contributors