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.

.. note::

   Pandas 0.23.2 is first pandas release that's compatible with
   Python 3.7 (:issue:`20552`)


.. 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`)
- Bug in both :meth:`DataFrame.first_valid_index` and :meth:`Series.first_valid_index` raised for a row index having duplicate values (:issue:`21441`)
-

.. _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:`HDFStore.groups` (and dependent functions like
  :meth:`~HDFStore.keys`.  (i.e. ``x in store`` checks are much faster)
  (:issue:`21372`)
- Improved performance of :meth:`MultiIndex.is_unique` (:issue:`21522`)
-

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

-
-

.. _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`)
- Bug in :meth:`DataFrame.drop` behaviour is not consistent for unique and non-unique indexes (:issue:`21494`)
- Bug in :func:`DataFrame.duplicated` with a large number of columns causing a 'maximum recursion depth exceeded' (:issue:`21524`).
-

**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`)
- Bug in :func:`json_normalize` when formatting the ``record_prefix`` with integer columns (:issue:`21536`)
- Bug in :meth:`detect_client_encoding` where potential ``IOError`` goes unhandled when importing in a mod_wsgi process due to restricted access to stdout. (:issue:`21552`)
-

**Plotting**

-
-

**Reshaping**

-
-

**Categorical**

- Bug in rendering :class:`Series` with ``Categorical`` dtype in rare conditions under Python 2.7 (:issue:`21002`)
-

**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**

-