v0.23.2.txt

.. _whatsnew_0232:

v0.23.2
-------

This is a minor bug-fix release in the 0.23.x series and includes some small regression fixes
and bug fixes. We recommend that all users upgrade to this version.

.. contents:: What's new in v0.23.2
    :local:
    :backlinks: none


.. _whatsnew_0232.fixed_regressions:

Fixed Regressions
~~~~~~~~~~~~~~~~~

- Fixed regression in :meth:`to_csv` when handling file-like object incorrectly (:issue:`21471`)
-

.. _whatsnew_0232.performance:

Performance Improvements
~~~~~~~~~~~~~~~~~~~~~~~~

- Improved performance of membership checks in :class:`CategoricalIndex`
  (i.e. ``x in ci``-style checks are much faster). :meth:`CategoricalIndex.contains`
  is likewise much faster (:issue:`21369`, :issue:`21508`)
- Improved performance of :meth:`MultiIndex.is_unique` (:issue:`21522`)
-

Documentation Changes
~~~~~~~~~~~~~~~~~~~~~

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.. _whatsnew_0232.bug_fixes:

Bug Fixes
~~~~~~~~~

**Groupby/Resample/Rolling**

-
-

**Timedelta**

- Bug in :class:`Timedelta` where non-zero timedeltas shorter than 1 microsecond were considered False (:issue:`21484`)

**Conversion**

- Bug in constructing :class:`Index` with an iterator or generator (:issue:`21470`)
- Bug in :meth:`Series.nlargest` for signed and unsigned integer dtypes when the minimum value is present (:issue:`21426`)


**Indexing**

- Bug in :meth:`Index.get_indexer_non_unique` with categorical key (:issue:`21448`)
- Bug in comparison operations for :class:`MultiIndex` where error was raised on equality / inequality comparison involving a MultiIndex with ``nlevels == 1`` (:issue:`21149`)
-

**I/O**

- Bug in :func:`read_csv` that caused it to incorrectly raise an error when ``nrows=0``, ``low_memory=True``, and ``index_col`` was not ``None`` (:issue:`21141`)
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-

**Plotting**

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**Reshaping**

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-

**Categorical**

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**Timezones**

- Bug in :class:`Timestamp` and :class:`DatetimeIndex` where passing a :class:`Timestamp` localized after a DST transition would return a datetime before the DST transition (:issue:`20854`)
- Bug in comparing :class:`DataFrame`s with tz-aware :class:`DatetimeIndex` columns with a DST transition that raised a ``KeyError`` (:issue:`19970`)
- Bug in :meth:`DatetimeIndex.shift` where an ``AssertionError`` would raise when shifting across DST (:issue:`8616`)
- Bug in :class:`Timestamp` constructor where passing an invalid timezone offset designator (``Z``) would not raise a ``ValueError``(:issue:`8910`)
- Bug in :meth:`Timestamp.replace` where replacing at a DST boundary would retain an incorrect offset (:issue:`7825`)
- Bug in :meth:`DatetimeIndex.reindex` when reindexing a tz-naive and tz-aware :class:`DatetimeIndex` (:issue:`8306`)
- Bug in :meth:`DatetimeIndex.resample` when downsampling across a DST boundary (:issue:`8531`)

**Other**

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