What's new in 1.2.3 (March 02, 2021)

These are the changes in pandas 1.2.3. See :ref:`release` for a full changelog including other versions of pandas.

Fixed regressions

Fixed regression in :meth:`~DataFrame.to_excel` raising KeyError when giving duplicate columns with columns attribute (:issue:`39695`)
Fixed regression in nullable integer unary ops propagating mask on assignment (:issue:`39943`)
Fixed regression in :meth:`DataFrame.__setitem__` not aligning :class:`DataFrame` on right-hand side for boolean indexer (:issue:`39931`)
Fixed regression in :meth:`~DataFrame.to_json` failing to use compression with URL-like paths that are internally opened in binary mode or with user-provided file objects that are opened in binary mode (:issue:`39985`)
Fixed regression in :meth:`Series.sort_index` and :meth:`DataFrame.sort_index`, which exited with an ungraceful error when having kwarg ascending=None passed. Passing ascending=None is still considered invalid, and the improved error message suggests a proper usage (ascending must be a boolean or a list-like of boolean) (:issue:`39434`)
Fixed regression in :meth:`DataFrame.transform` and :meth:`Series.transform` giving incorrect column labels when passed a dictionary with a mix of list and non-list values (:issue:`40018`)

.. contributors:: v1.2.2..v1.2.3