These are the changes in pandas 1.2.2. See Release notes for a full changelog including other versions of pandas.
Fixed regression in read_excel() that caused it to raise AttributeError when checking version of older xlrd versions (GH38955)
read_excel()
AttributeError
Fixed regression in DataFrame constructor reordering element when construction from datetime ndarray with dtype not "datetime64[ns]" (GH39422)
DataFrame
"datetime64[ns]"
Fixed regression in DataFrame.astype() and Series.astype() not casting to bytes dtype (GH39474)
DataFrame.astype()
Series.astype()
Fixed regression in to_pickle() failing to create bz2/xz compressed pickle files with protocol=5 (GH39002)
to_pickle()
protocol=5
Fixed regression in pandas.testing.assert_series_equal() and pandas.testing.assert_frame_equal() always raising AssertionError when comparing extension dtypes (GH39410)
pandas.testing.assert_series_equal()
pandas.testing.assert_frame_equal()
AssertionError
Fixed regression in to_csv() opening codecs.StreamWriter in binary mode instead of in text mode and ignoring user-provided mode (GH39247)
to_csv()
codecs.StreamWriter
mode
Fixed regression in Categorical.astype() casting to incorrect dtype when np.int32 is passed to dtype argument (GH39402)
Categorical.astype()
np.int32
Fixed regression in to_excel() creating corrupt files when appending (mode="a") to an existing file (GH39576)
to_excel()
mode="a"
Fixed regression in DataFrame.transform() failing in case of an empty DataFrame or Series (GH39636)
DataFrame.transform()
Fixed regression in groupby() or resample() when aggregating an all-NaN or numeric object dtype column (GH39329)
groupby()
resample()
Fixed regression in Rolling.count() where the min_periods argument would be set to 0 after the operation (GH39554)
Rolling.count()
min_periods
0
Fixed regression in read_excel() that incorrectly raised when the argument io was a non-path and non-buffer and the engine argument was specified (GH39528)
io
engine
pandas.read_excel() error message when a specified sheetname does not exist is now uniform across engines (GH39250)
pandas.read_excel()
sheetname
Fixed bug in pandas.read_excel() producing incorrect results when the engine openpyxl is used and the excel file is missing or has incorrect dimension information; the fix requires openpyxl >= 3.0.0, prior versions may still fail (GH38956, GH39001)
openpyxl
Fixed bug in pandas.read_excel() sometimes producing a DataFrame with trailing rows of np.nan when the engine openpyxl is used (GH39181)
np.nan
A total of 14 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.
Andrew Wieteska
Erfan Nariman
Joris Van den Bossche
Matthew Roeschke
MeeseeksMachine
Pandas Development Team
Pav A
Richard Shadrach
Simon Hawkins
Thomas Li
Torsten Wörtwein
Vladimir Podolskiy +
jbrockmendel
patrick