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v0.22.0.txt
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.. _whatsnew_0220:
v0.22.0
-------
This is a major release from 0.21.1 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.
.. _whatsnew_0220.enhancements:
New features
~~~~~~~~~~~~
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.. _whatsnew_0220.enhancements.merge_on_columns_and_levels:
Merging on a combination of columns and index levels
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Strings passed to :meth:`DataFrame.merge` as the ``on``, ``left_on``, and ``right_on``
parameters may now refer to either column names or index level names.
This enables merging ``DataFrame`` instances on a combination of index levels
and columns without resetting indexes. See the :ref:`Merge on columns and
levels <merging.merge_on_columns_and_levels>` documentation section.
(:issue:`14355`)
.. ipython:: python
left_index = pd.Index(['K0', 'K0', 'K1', 'K2'], name='key1')
left = pd.DataFrame({'A': ['A0', 'A1', 'A2', 'A3'],
'B': ['B0', 'B1', 'B2', 'B3'],
'key2': ['K0', 'K1', 'K0', 'K1']},
index=left_index)
right_index = pd.Index(['K0', 'K1', 'K2', 'K2'], name='key1')
right = pd.DataFrame({'C': ['C0', 'C1', 'C2', 'C3'],
'D': ['D0', 'D1', 'D2', 'D3'],
'key2': ['K0', 'K0', 'K0', 'K1']},
index=right_index)
left.merge(right, on=['key1', 'key2'])
.. _whatsnew_0220.enhancements.other:
Other Enhancements
^^^^^^^^^^^^^^^^^^
- Better support for ``Dataframe.style.to_excel()`` output with the ``xlsxwriter`` engine. (:issue:`16149`)
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.. _whatsnew_0220.api_breaking:
Backwards incompatible API changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. _whatsnew_0220.api:
Other API Changes
^^^^^^^^^^^^^^^^^
- ``NaT`` division with :class:`datetime.timedelta` will now return ``NaN`` instead of raising (:issue:`17876`)
- All-NaN levels in ``MultiIndex`` are now assigned float rather than object dtype, coherently with flat indexes (:issue:`17929`).
- :class:`Timestamp` will no longer silently ignore unused or invalid `tz` or `tzinfo` keyword arguments (:issue:`17690`)
- :class:`Timestamp` will no longer silently ignore invalid `freq` arguments (:issue:`5168`)
- :class:`CacheableOffset` and :class:`WeekDay` are no longer available in the `tseries.offsets` module (:issue:`17830`)
.. _whatsnew_0220.deprecations:
Deprecations
~~~~~~~~~~~~
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.. _whatsnew_0220.prior_deprecations:
Removal of prior version deprecations/changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. _whatsnew_0220.performance:
Performance Improvements
~~~~~~~~~~~~~~~~~~~~~~~~
- Indexers on Series or DataFrame no longer create a reference cycle (:issue:`17956`)
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.. _whatsnew_0220.docs:
Documentation Changes
~~~~~~~~~~~~~~~~~~~~~
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.. _whatsnew_0220.bug_fixes:
Bug Fixes
~~~~~~~~~
- Bug in ``pd.read_msgpack()`` with a non existent file is passed in Python 2 (:issue:`15296`)
- Bug in ``DataFrame.groupby`` where key as tuple in a ``MultiIndex`` were interpreted as a list of keys (:issue:`17979`)
- Bug in :func:`pd.read_csv` where a ``MultiIndex`` with duplicate columns was not being mangled appropriately (:issue:`18062`)
Conversion
^^^^^^^^^^
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Indexing
^^^^^^^^
- Bug in :func:`PeriodIndex.truncate` which raises ``TypeError`` when ``PeriodIndex`` is monotonic (:issue:`17717`)
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I/O
^^^
- :func:`read_html` now rewinds seekable IO objects after parse failure, before attempting to parse with a new parser. If a parser errors and the object is non-seekable, an informative error is raised suggesting the use of a different parser (:issue:`17975`)
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Plotting
^^^^^^^^
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Groupby/Resample/Rolling
^^^^^^^^^^^^^^^^^^^^^^^^
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Sparse
^^^^^^
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Reshaping
^^^^^^^^^
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Numeric
^^^^^^^
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Categorical
^^^^^^^^^^^
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Other
^^^^^
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