What’s new in 1.4.2 (April 2, 2022)#

These are the changes in pandas 1.4.2. See Release notes for a full changelog including other versions of pandas.

Fixed regressions#

Fixed regression in DataFrame.drop() and Series.drop() when Index had extension dtype and duplicates (GH45860)
Fixed regression in read_csv() killing python process when invalid file input was given for engine="c" (GH45957)
Fixed memory performance regression in Series.fillna() when called on a DataFrame column with inplace=True (GH46149)
Provided an alternative solution for passing custom Excel formats in Styler.to_excel(), which was a regression based on stricter CSS validation. Examples available in the documentation for Styler.format() (GH46152)
Fixed regression in DataFrame.replace() when a replacement value was also a target for replacement (GH46306)
Fixed regression in DataFrame.replace() when the replacement value was explicitly None when passed in a dictionary to to_replace (GH45601, GH45836)
Fixed regression when setting values with DataFrame.loc() losing MultiIndex names if DataFrame was empty before (GH46317)
Fixed regression when rendering boolean datatype columns with Styler() (GH46384)
Fixed regression in Groupby.rolling() with a frequency window that would raise a ValueError even if the datetimes within each group were monotonic (GH46061)

Fix some cases for subclasses that define their _constructor properties as general callables (GH46018)
Fixed “longtable” formatting in Styler.to_latex() when column_format is given in extended format (GH46037)
Fixed incorrect rendering in Styler.format() with hyperlinks="html" when the url contains a colon or other special characters (GH46389)
Improved error message in Rolling when window is a frequency and NaT is in the rolling axis (GH46087)

A total of 15 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.