What's new in 1.3.4 (October ??, 2021)

These are the changes in pandas 1.3.4. See :ref:`release` for a full changelog including other versions of pandas.

Fixed regressions

Fixed regression in :meth:`merge` with integer and NaN keys failing with outer merge (:issue:`43550`)
Fixed regression in :meth:`DataFrame.corr` raising ValueError with method="spearman" on 32-bit platforms (:issue:`43588`)
Fixed performance regression in :meth:`MultiIndex.equals` (:issue:`43549`)
Fixed performance regression in :meth:`.GroupBy.first` and :meth:`.GroupBy.last` with :class:`StringDtype` (:issue:`41596`)
Fixed regression in :meth:`Series.cat.reorder_categories` failing to update the categories on the Series (:issue:`43232`)
Fixed regression in :meth:`Series.cat.categories` setter failing to update the categories on the Series (:issue:`43334`)
Fixed regression in :meth:`pandas.read_csv` raising UnicodeDecodeError exception when memory_map=True (:issue:`43540`)
Fixed regression in :meth:`Series.aggregate` attempting to pass args and kwargs multiple times to the user supplied func in certain cases (:issue:`43357`)

Fixed bug in :meth:`.GroupBy.mean` with datetimelike values including NaT values returning incorrect results (:issue:`43132`)
Fixed bug in :meth:`Series.aggregate` not passing the first args to the user supplied func in certain cases (:issue:`43357`)

.. contributors:: v1.3.3..v1.3.4|HEAD