v0.21.1.txt

.. _whatsnew_0211:

v0.21.1
-------

This is a minor release from 0.21.1 and includes a number of deprecations, new
features, enhancements, and performance improvements along with a large number
of bug fixes. We recommend that all users upgrade to this version.

.. _whatsnew_0211.special:

Restore Matplotlib datetime Converter Registration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Pandas implements some matplotlib converters for nicely formatting the axis
labels on plots with ``datetime`` or ``Period`` values. Prior to pandas 0.21.0,
these were implicitly registered with matplotlib, as a side effect of
``import pandas``. In pandas 0.21.0, we required users to explicitly register
the converter.

.. code-block:: python

   >>> from pandas.plotting import register_matplotlib_converters
   >>> register_matplotlib_converters()

This caused problems for some users, so we're temporarily reverting that change;
pandas will again register the converters on import. Using the converters
without explicitly registering them will cause a ``FutureWarning``:

.. code-block:: python

   >>> import pandas as pd
   >>> import matplotlib.pyplot as plt
   >>> fig, ax = plt.subplots()
   >>> ax.plot(pd.Series(range(12), index=pd.date_range('2017', periods=12)))
   FutureWarning: Using an implicitly registered datetime converter for a
   matplotlib plotting method. The converter was registered by pandas on import.
   Future versions of pandas will require you to explicitly register matplotlib
   converters.
 
   To register the converters:
           >>> from pandas.plotting import register_matplotlib_converters
           >>> register_matplotlib_converters()

As the error message says, you'll need to register the converters if you intend
to use them with matplotlib plotting functions. Pandas plotting functions, such
as ``Series.plot``, will register them for you; calling ``register_converters``
first is not necessary.

We've added a new option to control the converters,
``pd.options.plotting.matplotlib.register_converters``. By default, they are
registered. Toggling this to ``False`` removes pandas' formatters (:issue:`18301`)

We're working with the matplotlib developers to make this easier. We're trying
to balance user convenience (automatically registering the converters) with
import performance and best practices (importing pandas shouldn't have the side
effect of overwriting any custom converters you've already set). Apologies for
any bumps along the way.

.. _whatsnew_0211.enhancements:

New features
~~~~~~~~~~~~

-
-
-

.. _whatsnew_0211.enhancements.other:

Other Enhancements
^^^^^^^^^^^^^^^^^^

- :meth:`Timestamp.timestamp` is now available in Python 2.7. (:issue:`17329`)
-
-

.. _whatsnew_0211.deprecations:

Deprecations
~~~~~~~~~~~~

- 
-
-

.. _whatsnew_0211.performance:

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

-
-
-

.. _whatsnew_0211.docs:

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

-
-
-

.. _whatsnew_0211.bug_fixes:

Bug Fixes
~~~~~~~~~
- Bug in ``DataFrame.resample(...).apply(...)`` when there is a callable that returns different columns (:issue:`15169`)
- Bug in :class:`TimedeltaIndex` subtraction could incorrectly overflow when ``NaT`` is present (:issue:`17791`)
- Bug in :class:`DatetimeIndex` subtracting datetimelike from DatetimeIndex could fail to overflow (:issue:`18020`)
- Bug in ``pd.Series.rolling.skew()`` and ``rolling.kurt()`` with all equal values has floating issue (:issue:`18044`)
- Bug in ``pd.DataFrameGroupBy.count()`` when counting over a datetimelike column (:issue:`13393`)
- Bug in ``pd.concat`` when empty and non-empty DataFrames or Series are concatenated (:issue:`18178` :issue:`18187`)

Conversion
^^^^^^^^^^

-
-
-

Indexing
^^^^^^^^

- Bug in a boolean comparison of a ``datetime.datetime`` and a ``datetime64[ns]`` dtype Series (:issue:`17965`)
- Bug where a ``MultiIndex`` with more than a million records was not raising ``AttributeError`` when trying to access a missing attribute (:issue:`18165`)
-
-

I/O
^^^

- Bug in class:`~pandas.io.stata.StataReader` not converting date/time columns with display formatting addressed (:issue:`17990`). Previously columns with display formatting were normally left as ordinal numbers and not converted to datetime objects.
- Bug in :func:`read_csv` when reading a compressed UTF-16 encoded file (:issue:`18071`)
- Bug in :func:`read_csv` for handling null values in index columns when specifying ``na_filter=False`` (:issue:`5239`)
- Bug in :meth:`DataFrame.to_csv` when the table had ``MultiIndex`` columns, and a list of strings was passed in for ``header`` (:issue:`5539`)
- :func:`read_parquet` now allows to specify the columns to read from a parquet file (:issue:`18154`)
- :func:`read_parquet` now allows to specify kwargs which are passed to the respective engine (:issue:`18216`)

Plotting
^^^^^^^^

-
-
-

Groupby/Resample/Rolling
^^^^^^^^^^^^^^^^^^^^^^^^

-
-
-

Sparse
^^^^^^

-
-
-

Reshaping
^^^^^^^^^

- Error message in ``pd.merge_asof()`` for key datatype mismatch now includes datatype of left and right key (:issue:`18068`)
-
-

Numeric
^^^^^^^

-
-
-

Categorical
^^^^^^^^^^^

- Bug in :meth:`DataFrame.astype` where casting to 'category' on an empty ``DataFrame`` causes a segmentation fault (:issue:`18004`)
- Error messages in the testing module have been improved when items have
  different ``CategoricalDtype`` (:issue:`18069`)
- ``CategoricalIndex`` can now correctly take a ``pd.api.types.CategoricalDtype`` as its dtype (:issue:`18116`)

Other
^^^^^

-
-
-