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v0.21.0.txt
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.. _whatsnew_0210:
v0.21.0 (???)
-------------
This is a major release from 0.20.x and includes a number of API changes, deprecations, new features,
enhancements, and performance improvements along with a large number of bug fixes. We recommend that all
users upgrade to this version.
Highlights include:
Check the :ref:`API Changes <whatsnew_0210.api_breaking>` and :ref:`deprecations <whatsnew_0210.deprecations>` before updating.
.. contents:: What's new in v0.21.0
:local:
:backlinks: none
.. _whatsnew_0210.enhancements:
New features
~~~~~~~~~~~~
- Support for `PEP 519 -- Adding a file system path protocol
<https://www.python.org/dev/peps/pep-0519/>`_ on most readers and writers (:issue:`13823`)
- Added `__fspath__` method to :class`:pandas.HDFStore`, :class:`pandas.ExcelFile`,
and :class:`pandas.ExcelWriter` to work properly with the file system path protocol (:issue:`13823`)
.. _whatsnew_0210.enhancements.other:
Other Enhancements
^^^^^^^^^^^^^^^^^^
- The ``validate`` argument for :func:`merge` function now checks whether a merge is one-to-one, one-to-many, many-to-one, or many-to-many. If a merge is found to not be an example of specified merge type, an exception of type ``MergeError`` will be raised. For more, see :ref:`here <merging.validation>` (:issue:`16270`)
- ``Series.to_dict()`` and ``DataFrame.to_dict()`` now support an ``into`` keyword which allows you to specify the ``collections.Mapping`` subclass that you would like returned. The default is ``dict``, which is backwards compatible. (:issue:`16122`)
- ``RangeIndex.append`` now returns a ``RangeIndex`` object when possible (:issue:`16212`)
- :func:`to_pickle` has gained a protocol parameter (:issue:`16252`). By default, this parameter is set to `HIGHEST_PROTOCOL <https://docs.python.org/3/library/pickle.html#data-stream-format>`__
- :func:`api.types.infer_dtype` now infers decimals. (:issue: `15690`)
- :func:`read_feather` has gained the ``nthreads`` parameter for multi-threaded operations (:issue:`16359`)
- :func:`DataFrame.clip()` and :func: `Series.cip()` have gained an inplace argument. (:issue: `15388`)
- :func:`crosstab` has gained a ``margins_name`` parameter to define the name of the row / column that will contain the totals when margins=True. (:issue:`15972`)
.. _whatsnew_0210.api_breaking:
Backwards incompatible API changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- Support has been dropped for Python 3.4 (:issue:`15251`)
- The Categorical constructor no longer accepts a scalar for the ``categories`` keyword. (:issue:`16022`)
- Accessing a non-existent attribute on a closed :class:`HDFStore` will now
raise an ``AttributeError`` rather than a ``ClosedFileError`` (:issue:`16301`)
- :func:`read_csv` now treats ``'null'`` strings as missing values by default (:issue:`16471`)
- :func:`read_csv` now treats ``'n/a'`` strings as missing values by default (:issue:`16078`)
- :class:`pandas.HDFStore`'s string representation is now faster and less detailed. For the previous behavior, use ``pandas.HDFStore.info()``. (:issue:`16503`).
.. _whatsnew_0210.api:
Other API Changes
^^^^^^^^^^^^^^^^^
- Moved definition of ``MergeError`` to the ``pandas.errors`` module.
.. _whatsnew_0210.deprecations:
Deprecations
~~~~~~~~~~~~
- :func:`read_excel()` has deprecated ``sheetname`` in favor of ``sheet_name`` for consistency with to_excel() (:issue:`10559`).
.. _whatsnew_0210.prior_deprecations:
Removal of prior version deprecations/changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- ``pd.read_excel()`` has dropped the ``has_index_names`` parameter (:issue:`10967`)
.. _whatsnew_0210.performance:
Performance Improvements
~~~~~~~~~~~~~~~~~~~~~~~~
.. _whatsnew_0210.bug_fixes:
Bug Fixes
~~~~~~~~~
Conversion
^^^^^^^^^^
Indexing
^^^^^^^^
I/O
^^^
- Bug in ``pd.read_csv()`` in which non integer values for the header argument generated an unhelpful / unrelated error message (:issue:`16338`)
Plotting
^^^^^^^^
Groupby/Resample/Rolling
^^^^^^^^^^^^^^^^^^^^^^^^
- Bug in ``infer_freq`` causing indices with 2-day gaps during the working week to be wrongly inferred as business daily (:issue:`16624`)
Sparse
^^^^^^
Reshaping
^^^^^^^^^
Numeric
^^^^^^^
Categorical
^^^^^^^^^^^
Other
^^^^^