.. _whatsnew_0130:

v0.13.0 (January 3, 2014)
---------------------------

{{ header }}



This is a major release from 0.12.0 and includes a number of API changes, several new features and
enhancements along with a large number of bug fixes.

Highlights include:

- support for a new index type ``Float64Index``, and other Indexing enhancements
- ``HDFStore`` has a new string based syntax for query specification
- support for new methods of interpolation
- updated ``timedelta`` operations
- a new string manipulation method ``extract``
- Nanosecond support for Offsets
- ``isin`` for DataFrames

Several experimental features are added, including:

- new ``eval/query`` methods for expression evaluation
- support for ``msgpack`` serialization
- an i/o interface to Google's ``BigQuery``

Their are several new or updated docs sections including:

- :ref:`Comparison with SQL<compare_with_sql>`, which should be useful for those familiar with SQL but still learning pandas.
- :ref:`Comparison with R<compare_with_r>`, idiom translations from R to pandas.
- :ref:`Enhancing Performance<enhancingperf>`, ways to enhance pandas performance with ``eval/query``.

.. warning::

   In 0.13.0 ``Series`` has internally been refactored to no longer sub-class ``ndarray``
   but instead subclass ``NDFrame``, similar to the rest of the pandas containers. This should be
   a transparent change with only very limited API implications. See :ref:`Internal Refactoring<whatsnew_0130.refactoring>`

API changes
~~~~~~~~~~~

- ``read_excel`` now supports an integer in its ``sheetname`` argument giving
  the index of the sheet to read in (:issue:`4301`).
- Text parser now treats anything that reads like inf ("inf", "Inf", "-Inf",
  "iNf", etc.) as infinity. (:issue:`4220`, :issue:`4219`), affecting
  ``read_table``, ``read_csv``, etc.
- ``pandas`` now is Python 2/3 compatible without the need for 2to3 thanks to
  @jtratner. As a result, pandas now uses iterators more extensively. This
  also led to the introduction of substantive parts of the Benjamin
  Peterson's ``six`` library into compat. (:issue:`4384`, :issue:`4375`,
  :issue:`4372`)
- ``pandas.util.compat`` and ``pandas.util.py3compat`` have been merged into
  ``pandas.compat``. ``pandas.compat`` now includes many functions allowing
  2/3 compatibility. It contains both list and iterator versions of range,
  filter, map and zip, plus other necessary elements for Python 3
  compatibility. ``lmap``, ``lzip``, ``lrange`` and ``lfilter`` all produce
  lists instead of iterators, for compatibility with ``numpy``, subscripting
  and ``pandas`` constructors.(:issue:`4384`, :issue:`4375`, :issue:`4372`)
- ``Series.get`` with negative indexers now returns the same as ``[]`` (:issue:`4390`)
- Changes to how ``Index`` and ``MultiIndex`` handle metadata (``levels``,
  ``labels``, and ``names``) (:issue:`4039`):

  .. code-block:: python

     # previously, you would have set levels or labels directly
     >>> pd.index.levels = [[1, 2, 3, 4], [1, 2, 4, 4]]

     # now, you use the set_levels or set_labels methods
     >>> index = pd.index.set_levels([[1, 2, 3, 4], [1, 2, 4, 4]])

     # similarly, for names, you can rename the object
     # but setting names is not deprecated
     >>> index = pd.index.set_names(["bob", "cranberry"])

     # and all methods take an inplace kwarg - but return None
     >>> pd.index.set_names(["bob", "cranberry"], inplace=True)

- **All** division with ``NDFrame`` objects is now *truedivision*, regardless
  of the future import. This means that operating on pandas objects will by default
  use *floating point* division, and return a floating point dtype.
  You can use ``//`` and ``floordiv`` to do integer division.

  Integer division

  .. code-block:: ipython

     In [3]: arr = np.array([1, 2, 3, 4])

     In [4]: arr2 = np.array([5, 3, 2, 1])

     In [5]: arr / arr2
     Out[5]: array([0, 0, 1, 4])

     In [6]: pd.Series(arr) // pd.Series(arr2)
     Out[6]:
     0    0
     1    0
     2    1
     3    4
     dtype: int64

  True Division

  .. code-block:: ipython

      In [7]: pd.Series(arr) / pd.Series(arr2)  # no future import required
      Out[7]:
      0    0.200000
      1    0.666667
      2    1.500000
      3    4.000000
      dtype: float64

- Infer and downcast dtype if ``downcast='infer'`` is passed to ``fillna/ffill/bfill`` (:issue:`4604`)
- ``__nonzero__`` for all NDFrame objects, will now raise a ``ValueError``, this reverts back to (:issue:`1073`, :issue:`4633`)
  behavior. See :ref:`gotchas<gotchas.truth>` for a more detailed discussion.

  This prevents doing boolean comparison on *entire* pandas objects, which is inherently ambiguous. These all will raise a ``ValueError``.

  .. code-block:: python

     >>> df = pd.DataFrame({'A': np.random.randn(10),
     ...                    'B': np.random.randn(10),
     ...                    'C': pd.date_range('20130101', periods=10)
     ...                    })
     ...
     >>> if df:
     ...     pass
     ...
     Traceback (most recent call last):
         ...
     ValueError: The truth value of a DataFrame is ambiguous.  Use a.empty,
     a.bool(), a.item(), a.any() or a.all().

     >>> df1 = df
     >>> df2 = df
     >>> df1 and df2
     Traceback (most recent call last):
         ...
     ValueError: The truth value of a DataFrame is ambiguous.  Use a.empty,
     a.bool(), a.item(), a.any() or a.all().

     >>> d = [1, 2, 3]
     >>> s1 = pd.Series(d)
     >>> s2 = pd.Series(d)
     >>> s1 and s2
     Traceback (most recent call last):
         ...
     ValueError: The truth value of a DataFrame is ambiguous.  Use a.empty,
     a.bool(), a.item(), a.any() or a.all().

  Added the ``.bool()`` method to ``NDFrame`` objects to facilitate evaluating of single-element boolean Series:

  .. ipython:: python

     pd.Series([True]).bool()
     pd.Series([False]).bool()
     pd.DataFrame([[True]]).bool()
     pd.DataFrame([[False]]).bool()

- All non-Index NDFrames (``Series``, ``DataFrame``, ``Panel``, ``Panel4D``,
  ``SparsePanel``, etc.), now support the entire set of arithmetic operators
  and arithmetic flex methods (add, sub, mul, etc.). ``SparsePanel`` does not
  support ``pow`` or ``mod`` with non-scalars. (:issue:`3765`)
- ``Series`` and ``DataFrame`` now have a ``mode()`` method to calculate the
  statistical mode(s) by axis/Series. (:issue:`5367`)

- Chained assignment will now by default warn if the user is assigning to a copy. This can be changed
  with the option ``mode.chained_assignment``, allowed options are ``raise/warn/None``. See :ref:`the docs<indexing.view_versus_copy>`.

  .. ipython:: python

     dfc = pd.DataFrame({'A': ['aaa', 'bbb', 'ccc'], 'B': [1, 2, 3]})
     pd.set_option('chained_assignment', 'warn')

  The following warning / exception will show if this is attempted.

  .. ipython:: python
     :okwarning:

     dfc.loc[0]['A'] = 1111

  ::

     Traceback (most recent call last)
        ...
     SettingWithCopyWarning:
        A value is trying to be set on a copy of a slice from a DataFrame.
        Try using .loc[row_index,col_indexer] = value instead

  Here is the correct method of assignment.

  .. ipython:: python

     dfc.loc[0, 'A'] = 11
     dfc

- ``Panel.reindex`` has the following call signature ``Panel.reindex(items=None, major_axis=None, minor_axis=None, **kwargs)``
   to conform with other ``NDFrame`` objects. See :ref:`Internal Refactoring<whatsnew_0130.refactoring>` for more information.

- ``Series.argmin`` and ``Series.argmax`` are now aliased to ``Series.idxmin`` and ``Series.idxmax``. These return the *index* of the
   min or max element respectively. Prior to 0.13.0 these would return the position of the min / max element. (:issue:`6214`)

Prior version deprecations/changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These were announced changes in 0.12 or prior that are taking effect as of 0.13.0

- Remove deprecated ``Factor`` (:issue:`3650`)
- Remove deprecated ``set_printoptions/reset_printoptions`` (:issue:`3046`)
- Remove deprecated ``_verbose_info`` (:issue:`3215`)
- Remove deprecated ``read_clipboard/to_clipboard/ExcelFile/ExcelWriter`` from ``pandas.io.parsers`` (:issue:`3717`)
  These are available as functions in the main pandas namespace (e.g. ``pd.read_clipboard``)
- default for ``tupleize_cols`` is now ``False`` for both ``to_csv`` and ``read_csv``. Fair warning in 0.12 (:issue:`3604`)
- default for `display.max_seq_len` is now 100 rather then `None`. This activates
  truncated display ("...") of long sequences in various places. (:issue:`3391`)

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

Deprecated in 0.13.0

- deprecated ``iterkv``, which will be removed in a future release (this was
  an alias of iteritems used to bypass ``2to3``'s changes).
  (:issue:`4384`, :issue:`4375`, :issue:`4372`)
- deprecated the string method ``match``, whose role is now performed more
  idiomatically by ``extract``. In a future release, the default behavior
  of ``match`` will change to become analogous to ``contains``, which returns
  a boolean indexer. (Their
  distinction is strictness: ``match`` relies on ``re.match`` while
  ``contains`` relies on ``re.search``.) In this release, the deprecated
  behavior is the default, but the new behavior is available through the
  keyword argument ``as_indexer=True``.

Indexing API changes
~~~~~~~~~~~~~~~~~~~~

Prior to 0.13, it was impossible to use a label indexer (``.loc/.ix``) to set a value that
was not contained in the index of a particular axis. (:issue:`2578`). See :ref:`the docs<indexing.basics.partial_setting>`

In the ``Series`` case this is effectively an appending operation

.. ipython:: python

   s = pd.Series([1, 2, 3])
   s
   s[5] = 5.
   s

.. ipython:: python

   dfi = pd.DataFrame(np.arange(6).reshape(3, 2),
                      columns=['A', 'B'])
   dfi

This would previously ``KeyError``

.. ipython:: python

   dfi.loc[:, 'C'] = dfi.loc[:, 'A']
   dfi

This is like an ``append`` operation.

.. ipython:: python

   dfi.loc[3] = 5
   dfi

A Panel setting operation on an arbitrary axis aligns the input to the Panel

.. code-block:: ipython

   In [20]: p = pd.Panel(np.arange(16).reshape(2, 4, 2),
      ....:              items=['Item1', 'Item2'],
      ....:              major_axis=pd.date_range('2001/1/12', periods=4),
      ....:              minor_axis=['A', 'B'], dtype='float64')
      ....:

   In [21]: p
   Out[21]:
   <class 'pandas.core.panel.Panel'>
   Dimensions: 2 (items) x 4 (major_axis) x 2 (minor_axis)
   Items axis: Item1 to Item2
   Major_axis axis: 2001-01-12 00:00:00 to 2001-01-15 00:00:00
   Minor_axis axis: A to B

   In [22]: p.loc[:, :, 'C'] = pd.Series([30, 32], index=p.items)

   In [23]: p
   Out[23]:
   <class 'pandas.core.panel.Panel'>
   Dimensions: 2 (items) x 4 (major_axis) x 3 (minor_axis)
   Items axis: Item1 to Item2
   Major_axis axis: 2001-01-12 00:00:00 to 2001-01-15 00:00:00
   Minor_axis axis: A to C

   In [24]: p.loc[:, :, 'C']
   Out[24]:
               Item1  Item2
   2001-01-12   30.0   32.0
   2001-01-13   30.0   32.0
   2001-01-14   30.0   32.0
   2001-01-15   30.0   32.0

Float64Index API change
~~~~~~~~~~~~~~~~~~~~~~~

- Added a new index type, ``Float64Index``. This will be automatically created when passing floating values in index creation.
  This enables a pure label-based slicing paradigm that makes ``[],ix,loc`` for scalar indexing and slicing work exactly the
  same. See :ref:`the docs<indexing.float64index>`, (:issue:`263`)

  Construction is by default for floating type values.

  .. ipython:: python

     index = pd.Index([1.5, 2, 3, 4.5, 5])
     index
     s = pd.Series(range(5), index=index)
     s

  Scalar selection for ``[],.ix,.loc`` will always be label based. An integer will match an equal float index (e.g. ``3`` is equivalent to ``3.0``)

  .. ipython:: python

     s[3]
     s.loc[3]

  The only positional indexing is via ``iloc``

  .. ipython:: python

     s.iloc[3]

  A scalar index that is not found will raise ``KeyError``

  Slicing is ALWAYS on the values of the index, for ``[],ix,loc`` and ALWAYS positional with ``iloc``

  .. ipython:: python

     s[2:4]
     s.loc[2:4]
     s.iloc[2:4]

  In float indexes, slicing using floats are allowed

  .. ipython:: python

     s[2.1:4.6]
     s.loc[2.1:4.6]

- Indexing on other index types are preserved (and positional fallback for ``[],ix``), with the exception, that floating point slicing
  on indexes on non ``Float64Index`` will now raise a ``TypeError``.

  .. code-block:: ipython

     In [1]: pd.Series(range(5))[3.5]
     TypeError: the label [3.5] is not a proper indexer for this index type (Int64Index)

     In [1]: pd.Series(range(5))[3.5:4.5]
     TypeError: the slice start [3.5] is not a proper indexer for this index type (Int64Index)

  Using a scalar float indexer will be deprecated in a future version, but is allowed for now.

  .. code-block:: ipython

     In [3]: pd.Series(range(5))[3.0]
     Out[3]: 3

HDFStore API changes
~~~~~~~~~~~~~~~~~~~~

- Query Format Changes. A much more string-like query format is now supported. See :ref:`the docs<io.hdf5-query>`.

  .. ipython:: python

     path = 'test.h5'
     dfq = pd.DataFrame(np.random.randn(10, 4),
                        columns=list('ABCD'),
                        index=pd.date_range('20130101', periods=10))
     dfq.to_hdf(path, 'dfq', format='table', data_columns=True)

  Use boolean expressions, with in-line function evaluation.

  .. ipython:: python

     pd.read_hdf(path, 'dfq',
                 where="index>Timestamp('20130104') & columns=['A', 'B']")

  Use an inline column reference

  .. ipython:: python

     pd.read_hdf(path, 'dfq',
                 where="A>0 or C>0")

  .. ipython:: python
     :suppress:

     import os
     os.remove(path)

- the ``format`` keyword now replaces the ``table`` keyword; allowed values are ``fixed(f)`` or ``table(t)``
  the same defaults as prior < 0.13.0 remain, e.g. ``put`` implies ``fixed`` format and ``append`` implies
  ``table`` format. This default format can be set as an option by setting ``io.hdf.default_format``.

  .. ipython:: python

     path = 'test.h5'
     df = pd.DataFrame(np.random.randn(10, 2))
     df.to_hdf(path, 'df_table', format='table')
     df.to_hdf(path, 'df_table2', append=True)
     df.to_hdf(path, 'df_fixed')
     with pd.HDFStore(path) as store:
         print(store)

  .. ipython:: python
     :suppress:

     import os
     os.remove(path)

- Significant table writing performance improvements
- handle a passed ``Series`` in table format (:issue:`4330`)
- can now serialize a ``timedelta64[ns]`` dtype in a table (:issue:`3577`), See :ref:`the docs<io.hdf5-timedelta>`.
- added an ``is_open`` property to indicate if the underlying file handle is_open;
  a closed store will now report 'CLOSED' when viewing the store (rather than raising an error)
  (:issue:`4409`)
- a close of a ``HDFStore`` now will close that instance of the ``HDFStore``
  but will only close the actual file if the ref count (by ``PyTables``) w.r.t. all of the open handles
  are 0. Essentially you have a local instance of ``HDFStore`` referenced by a variable. Once you
  close it, it will report closed. Other references (to the same file) will continue to operate
  until they themselves are closed. Performing an action on a closed file will raise
  ``ClosedFileError``

  .. ipython:: python

     path = 'test.h5'
     df = pd.DataFrame(np.random.randn(10, 2))
     store1 = pd.HDFStore(path)
     store2 = pd.HDFStore(path)
     store1.append('df', df)
     store2.append('df2', df)

     store1
     store2
     store1.close()
     store2
     store2.close()
     store2

  .. ipython:: python
     :suppress:

     import os
     os.remove(path)

- removed the ``_quiet`` attribute, replace by a ``DuplicateWarning`` if retrieving
  duplicate rows from a table (:issue:`4367`)
- removed the ``warn`` argument from ``open``. Instead a ``PossibleDataLossError`` exception will
  be raised if you try to use ``mode='w'`` with an OPEN file handle (:issue:`4367`)
- allow a passed locations array or mask as a ``where`` condition (:issue:`4467`).
  See :ref:`the docs<io.hdf5-where_mask>` for an example.
- add the keyword ``dropna=True`` to ``append`` to change whether ALL nan rows are not written
  to the store (default is ``True``, ALL nan rows are NOT written), also settable
  via the option ``io.hdf.dropna_table`` (:issue:`4625`)
- pass through store creation arguments; can be used to support in-memory stores

DataFrame repr changes
~~~~~~~~~~~~~~~~~~~~~~

The HTML and plain text representations of :class:`DataFrame` now show
a truncated view of the table once it exceeds a certain size, rather
than switching to the short info view (:issue:`4886`, :issue:`5550`).
This makes the representation more consistent as small DataFrames get
larger.

.. image:: ../_static/df_repr_truncated.png
   :alt: Truncated HTML representation of a DataFrame

To get the info view, call :meth:`DataFrame.info`. If you prefer the
info view as the repr for large DataFrames, you can set this by running
``set_option('display.large_repr', 'info')``.

Enhancements
~~~~~~~~~~~~

- ``df.to_clipboard()`` learned a new ``excel`` keyword that let's you
  paste df data directly into excel (enabled by default). (:issue:`5070`).
- ``read_html`` now raises a ``URLError`` instead of catching and raising a
  ``ValueError`` (:issue:`4303`, :issue:`4305`)
- Added a test for ``read_clipboard()`` and ``to_clipboard()`` (:issue:`4282`)
- Clipboard functionality now works with PySide (:issue:`4282`)
- Added a more informative error message when plot arguments contain
  overlapping color and style arguments (:issue:`4402`)
- ``to_dict`` now takes ``records`` as a possible out type.  Returns an array
  of column-keyed dictionaries. (:issue:`4936`)

- ``NaN`` handing in get_dummies (:issue:`4446`) with `dummy_na`

  .. ipython:: python

     # previously, nan was erroneously counted as 2 here
     # now it is not counted at all
     pd.get_dummies([1, 2, np.nan])

     # unless requested
     pd.get_dummies([1, 2, np.nan], dummy_na=True)


- ``timedelta64[ns]`` operations. See :ref:`the docs<timedeltas.timedeltas_convert>`.

  .. warning::

     Most of these operations require ``numpy >= 1.7``

  Using the new top-level ``to_timedelta``, you can convert a scalar or array from the standard
  timedelta format (produced by ``to_csv``) into a timedelta type (``np.timedelta64`` in ``nanoseconds``).

  .. ipython:: python

     pd.to_timedelta('1 days 06:05:01.00003')
     pd.to_timedelta('15.5us')
     pd.to_timedelta(['1 days 06:05:01.00003', '15.5us', 'nan'])
     pd.to_timedelta(np.arange(5), unit='s')
     pd.to_timedelta(np.arange(5), unit='d')

  A Series of dtype ``timedelta64[ns]`` can now be divided by another
  ``timedelta64[ns]`` object, or astyped to yield a ``float64`` dtyped Series. This
  is frequency conversion. See :ref:`the docs<timedeltas.timedeltas_convert>` for the docs.

  .. ipython:: python

     import datetime
     td = pd.Series(pd.date_range('20130101', periods=4)) - pd.Series(
         pd.date_range('20121201', periods=4))
     td[2] += np.timedelta64(datetime.timedelta(minutes=5, seconds=3))
     td[3] = np.nan
     td

     # to days
     td / np.timedelta64(1, 'D')
     td.astype('timedelta64[D]')

     # to seconds
     td / np.timedelta64(1, 's')
     td.astype('timedelta64[s]')

  Dividing or multiplying a ``timedelta64[ns]`` Series by an integer or integer Series

  .. ipython:: python

     td * -1
     td * pd.Series([1, 2, 3, 4])

  Absolute ``DateOffset`` objects can act equivalently to ``timedeltas``

  .. ipython:: python

     from pandas import offsets
     td + offsets.Minute(5) + offsets.Milli(5)

  Fillna is now supported for timedeltas

  .. ipython:: python

     td.fillna(pd.Timedelta(0))
     td.fillna(datetime.timedelta(days=1, seconds=5))

  You can do numeric reduction operations on timedeltas.

  .. ipython:: python

     td.mean()
     td.quantile(.1)

- ``plot(kind='kde')`` now accepts the optional parameters ``bw_method`` and
  ``ind``, passed to scipy.stats.gaussian_kde() (for scipy >= 0.11.0) to set
  the bandwidth, and to gkde.evaluate() to specify the indices at which it
  is evaluated, respectively. See scipy docs. (:issue:`4298`)

- DataFrame constructor now accepts a numpy masked record array (:issue:`3478`)

- The new vectorized string method ``extract`` return regular expression
  matches more conveniently.

  .. ipython:: python
     :okwarning:

     pd.Series(['a1', 'b2', 'c3']).str.extract('[ab](\\d)')

  Elements that do not match return ``NaN``. Extracting a regular expression
  with more than one group returns a DataFrame with one column per group.


  .. ipython:: python
     :okwarning:

     pd.Series(['a1', 'b2', 'c3']).str.extract('([ab])(\\d)')

  Elements that do not match return a row of ``NaN``.
  Thus, a Series of messy strings can be *converted* into a
  like-indexed Series or DataFrame of cleaned-up or more useful strings,
  without necessitating ``get()`` to access tuples or ``re.match`` objects.

  Named groups like

  .. ipython:: python
     :okwarning:

     pd.Series(['a1', 'b2', 'c3']).str.extract(
         '(?P<letter>[ab])(?P<digit>\\d)')

  and optional groups can also be used.

  .. ipython:: python
     :okwarning:

      pd.Series(['a1', 'b2', '3']).str.extract(
          '(?P<letter>[ab])?(?P<digit>\\d)')

- ``read_stata`` now accepts Stata 13 format (:issue:`4291`)

- ``read_fwf`` now infers the column specifications from the first 100 rows of
  the file if the data has correctly separated and properly aligned columns
  using the delimiter provided to the function (:issue:`4488`).

- support for nanosecond times as an offset

  .. warning::

     These operations require ``numpy >= 1.7``

  Period conversions in the range of seconds and below were reworked and extended
  up to nanoseconds. Periods in the nanosecond range are now available.

  .. ipython:: python

     pd.date_range('2013-01-01', periods=5, freq='5N')

  or with frequency as offset

  .. ipython:: python

     pd.date_range('2013-01-01', periods=5, freq=pd.offsets.Nano(5))

  Timestamps can be modified in the nanosecond range

  .. ipython:: python

     t = pd.Timestamp('20130101 09:01:02')
     t + pd.tseries.offsets.Nano(123)

- A new method, ``isin`` for DataFrames, which plays nicely with boolean indexing. The argument to ``isin``, what we're comparing the DataFrame to, can be a DataFrame, Series, dict, or array of values. See :ref:`the docs<indexing.basics.indexing_isin>` for more.

  To get the rows where any of the conditions are met:

  .. ipython:: python

     dfi = pd.DataFrame({'A': [1, 2, 3, 4], 'B': ['a', 'b', 'f', 'n']})
     dfi
     other = pd.DataFrame({'A': [1, 3, 3, 7], 'B': ['e', 'f', 'f', 'e']})
     mask = dfi.isin(other)
     mask
     dfi[mask.any(1)]

- ``Series`` now supports a ``to_frame`` method to convert it to a single-column DataFrame (:issue:`5164`)

- All R datasets listed here http://stat.ethz.ch/R-manual/R-devel/library/datasets/html/00Index.html can now be loaded into Pandas objects

  .. code-block:: python

     # note that pandas.rpy was deprecated in v0.16.0
     import pandas.rpy.common as com
     com.load_data('Titanic')

- ``tz_localize`` can infer a fall daylight savings transition based on the structure
  of the unlocalized data (:issue:`4230`), see :ref:`the docs<timeseries.timezone>`

- ``DatetimeIndex`` is now in the API documentation, see :ref:`the docs<api.datetimeindex>`

- :meth:`~pandas.io.json.json_normalize` is a new method to allow you to create a flat table
  from semi-structured JSON data. See :ref:`the docs<io.json_normalize>` (:issue:`1067`)

- Added PySide support for the qtpandas DataFrameModel and DataFrameWidget.

- Python csv parser now supports usecols (:issue:`4335`)

- Frequencies gained several new offsets:

  * ``LastWeekOfMonth`` (:issue:`4637`)
  * ``FY5253``, and ``FY5253Quarter`` (:issue:`4511`)


- DataFrame has a new ``interpolate`` method, similar to Series (:issue:`4434`, :issue:`1892`)

  .. ipython:: python

      df = pd.DataFrame({'A': [1, 2.1, np.nan, 4.7, 5.6, 6.8],
                        'B': [.25, np.nan, np.nan, 4, 12.2, 14.4]})
      df.interpolate()

  Additionally, the ``method`` argument to ``interpolate`` has been expanded
  to include ``'nearest', 'zero', 'slinear', 'quadratic', 'cubic',
  'barycentric', 'krogh', 'piecewise_polynomial', 'pchip', 'polynomial', 'spline'``
  The new methods require scipy_. Consult the Scipy reference guide_ and documentation_ for more information
  about when the various methods are appropriate. See :ref:`the docs<missing_data.interpolate>`.

  Interpolate now also accepts a ``limit`` keyword argument.
  This works similar to ``fillna``'s limit:

  .. ipython:: python

    ser = pd.Series([1, 3, np.nan, np.nan, np.nan, 11])
    ser.interpolate(limit=2)

- Added ``wide_to_long`` panel data convenience function. See :ref:`the docs<reshaping.melt>`.

  .. ipython:: python

    np.random.seed(123)
    df = pd.DataFrame({"A1970" : {0 : "a", 1 : "b", 2 : "c"},
                       "A1980" : {0 : "d", 1 : "e", 2 : "f"},
                       "B1970" : {0 : 2.5, 1 : 1.2, 2 : .7},
                       "B1980" : {0 : 3.2, 1 : 1.3, 2 : .1},
                       "X"     : dict(zip(range(3), np.random.randn(3)))
                      })
    df["id"] = df.index
    df
    pd.wide_to_long(df, ["A", "B"], i="id", j="year")

.. _scipy: http://www.scipy.org
.. _documentation: http://docs.scipy.org/doc/scipy/reference/interpolate.html#univariate-interpolation
.. _guide: http://docs.scipy.org/doc/scipy/reference/tutorial/interpolate.html

- ``to_csv`` now takes a ``date_format`` keyword argument that specifies how
  output datetime objects should be formatted. Datetimes encountered in the
  index, columns, and values will all have this formatting applied. (:issue:`4313`)
- ``DataFrame.plot`` will scatter plot x versus y by passing ``kind='scatter'`` (:issue:`2215`)
- Added support for Google Analytics v3 API segment IDs that also supports v2 IDs. (:issue:`5271`)

.. _whatsnew_0130.experimental:

Experimental
~~~~~~~~~~~~

- The new :func:`~pandas.eval` function implements expression evaluation using
  ``numexpr`` behind the scenes. This results in large speedups for
  complicated expressions involving large DataFrames/Series. For example,

  .. ipython:: python

     nrows, ncols = 20000, 100
     df1, df2, df3, df4 = [pd.DataFrame(np.random.randn(nrows, ncols))
                           for _ in range(4)]

  .. ipython:: python

     # eval with NumExpr backend
     %timeit pd.eval('df1 + df2 + df3 + df4')

  .. ipython:: python

     # pure Python evaluation
     %timeit df1 + df2 + df3 + df4

  For more details, see the :ref:`the docs<enhancingperf.eval>`

- Similar to ``pandas.eval``, :class:`~pandas.DataFrame` has a new
  ``DataFrame.eval`` method that evaluates an expression in the context of
  the ``DataFrame``. For example,

  .. ipython:: python
     :suppress:

     try:
         del a  # noqa: F821
     except NameError:
         pass

     try:
         del b  # noqa: F821
     except NameError:
         pass

  .. ipython:: python

     df = pd.DataFrame(np.random.randn(10, 2), columns=['a', 'b'])
     df.eval('a + b')

- :meth:`~pandas.DataFrame.query` method has been added that allows
  you to select elements of a ``DataFrame`` using a natural query syntax
  nearly identical to Python syntax. For example,

  .. ipython:: python
     :suppress:

     try:
         del a  # noqa: F821
     except NameError:
         pass

     try:
         del b  # noqa: F821
     except NameError:
         pass

     try:
         del c  # noqa: F821
     except NameError:
         pass

  .. ipython:: python

     n = 20
     df = pd.DataFrame(np.random.randint(n, size=(n, 3)), columns=['a', 'b', 'c'])
     df.query('a < b < c')

  selects all the rows of ``df`` where ``a < b < c`` evaluates to ``True``.
  For more details see the :ref:`the docs<indexing.query>`.

- ``pd.read_msgpack()`` and ``pd.to_msgpack()`` are now a supported method of serialization
  of arbitrary pandas (and python objects) in a lightweight portable binary format. See :ref:`the docs<io.msgpack>`

  .. warning::

     Since this is an EXPERIMENTAL LIBRARY, the storage format may not be stable until a future release.

  .. code-block:: python

     df = pd.DataFrame(np.random.rand(5, 2), columns=list('AB'))
     df.to_msgpack('foo.msg')
     pd.read_msgpack('foo.msg')

     s = pd.Series(np.random.rand(5), index=pd.date_range('20130101', periods=5))
     pd.to_msgpack('foo.msg', df, s)
     pd.read_msgpack('foo.msg')

  You can pass ``iterator=True`` to iterator over the unpacked results

  .. code-block:: python

     for o in pd.read_msgpack('foo.msg', iterator=True):
         print(o)

  .. ipython:: python
     :suppress:
     :okexcept:

     os.remove('foo.msg')

- ``pandas.io.gbq`` provides a simple way to extract from, and load data into,
  Google's BigQuery Data Sets by way of pandas DataFrames. BigQuery is a high
  performance SQL-like database service, useful for performing ad-hoc queries
  against extremely large datasets. :ref:`See the docs <io.bigquery>`

  .. code-block:: python

     from pandas.io import gbq

     # A query to select the average monthly temperatures in the
     # in the year 2000 across the USA. The dataset,
     # publicata:samples.gsod, is available on all BigQuery accounts,
     # and is based on NOAA gsod data.

     query = """SELECT station_number as STATION,
     month as MONTH, AVG(mean_temp) as MEAN_TEMP
     FROM publicdata:samples.gsod
     WHERE YEAR = 2000
     GROUP BY STATION, MONTH
     ORDER BY STATION, MONTH ASC"""

     # Fetch the result set for this query

     # Your Google BigQuery Project ID
     # To find this, see your dashboard:
     # https://console.developers.google.com/iam-admin/projects?authuser=0
     projectid = 'xxxxxxxxx'
     df = gbq.read_gbq(query, project_id=projectid)

     # Use pandas to process and reshape the dataset

     df2 = df.pivot(index='STATION', columns='MONTH', values='MEAN_TEMP')
     df3 = pd.concat([df2.min(), df2.mean(), df2.max()],
                     axis=1, keys=["Min Tem", "Mean Temp", "Max Temp"])

  The resulting DataFrame is::

     > df3
                 Min Tem  Mean Temp    Max Temp
      MONTH
      1     -53.336667  39.827892   89.770968
      2     -49.837500  43.685219   93.437932
      3     -77.926087  48.708355   96.099998
      4     -82.892858  55.070087   97.317240
      5     -92.378261  61.428117  102.042856
      6     -77.703334  65.858888  102.900000
      7     -87.821428  68.169663  106.510714
      8     -89.431999  68.614215  105.500000
      9     -86.611112  63.436935  107.142856
      10    -78.209677  56.880838   92.103333
      11    -50.125000  48.861228   94.996428
      12    -50.332258  42.286879   94.396774

  .. warning::

     To use this module, you will need a BigQuery account. See
     <https://cloud.google.com/products/big-query> for details.

     As of 10/10/13, there is a bug in Google's API preventing result sets
     from being larger than 100,000 rows. A patch is scheduled for the week of
     10/14/13.

.. _whatsnew_0130.refactoring:

Internal refactoring
~~~~~~~~~~~~~~~~~~~~

In 0.13.0 there is a major refactor primarily to subclass ``Series`` from
``NDFrame``, which is the base class currently for ``DataFrame`` and ``Panel``,
to unify methods and behaviors. Series formerly subclassed directly from
``ndarray``. (:issue:`4080`, :issue:`3862`, :issue:`816`)

.. warning::

   There are two potential incompatibilities from < 0.13.0

   - Using certain numpy functions would previously return a ``Series`` if passed a ``Series``
     as an argument. This seems only to affect ``np.ones_like``, ``np.empty_like``,
     ``np.diff`` and ``np.where``. These now return ``ndarrays``.

     .. ipython:: python

        s = pd.Series([1, 2, 3, 4])

     Numpy Usage

     .. ipython:: python

        np.ones_like(s)
        np.diff(s)
        np.where(s > 1, s, np.nan)

     Pandonic Usage

     .. ipython:: python

        pd.Series(1, index=s.index)
        s.diff()
        s.where(s > 1)

   - Passing a ``Series`` directly to a cython function expecting an ``ndarray`` type will no
     long work directly, you must pass ``Series.values``, See :ref:`Enhancing Performance<enhancingperf.ndarray>`

   - ``Series(0.5)`` would previously return the scalar ``0.5``, instead this will return a 1-element ``Series``

   - This change breaks ``rpy2<=2.3.8``. an Issue has been opened against rpy2 and a workaround
     is detailed in :issue:`5698`. Thanks @JanSchulz.

- Pickle compatibility is preserved for pickles created prior to 0.13. These must be unpickled with ``pd.read_pickle``, see :ref:`Pickling<io.pickle>`.

- Refactor of series.py/frame.py/panel.py to move common code to generic.py

  - added ``_setup_axes`` to created generic NDFrame structures
  - moved methods

    - ``from_axes,_wrap_array,axes,ix,loc,iloc,shape,empty,swapaxes,transpose,pop``
    - ``__iter__,keys,__contains__,__len__,__neg__,__invert__``
    - ``convert_objects,as_blocks,as_matrix,values``
    - ``__getstate__,__setstate__`` (compat remains in frame/panel)
    - ``__getattr__,__setattr__``
    - ``_indexed_same,reindex_like,align,where,mask``
    - ``fillna,replace`` (``Series`` replace is now consistent with ``DataFrame``)
    - ``filter`` (also added axis argument to selectively filter on a different axis)
    - ``reindex,reindex_axis,take``
    - ``truncate`` (moved to become part of ``NDFrame``)

- These are API changes which make ``Panel`` more consistent with ``DataFrame``

  - ``swapaxes`` on a ``Panel`` with the same axes specified now return a copy
  - support attribute access for setting
  - filter supports the same API as the original ``DataFrame`` filter

- Reindex called with no arguments will now return a copy of the input object

- ``TimeSeries`` is now an alias for ``Series``. the property ``is_time_series``
  can be used to distinguish (if desired)

- Refactor of Sparse objects to use BlockManager

  - Created a new block type in internals, ``SparseBlock``, which can hold multi-dtypes
    and is non-consolidatable. ``SparseSeries`` and ``SparseDataFrame`` now inherit
    more methods from there hierarchy (Series/DataFrame), and no longer inherit
    from ``SparseArray`` (which instead is the object of the ``SparseBlock``)
  - Sparse suite now supports integration with non-sparse data. Non-float sparse
    data is supportable (partially implemented)
  - Operations on sparse structures within DataFrames should preserve sparseness,
    merging type operations will convert to dense (and back to sparse), so might
    be somewhat inefficient
  - enable setitem on ``SparseSeries`` for boolean/integer/slices
  - ``SparsePanels`` implementation is unchanged (e.g. not using BlockManager, needs work)

- added ``ftypes`` method to Series/DataFrame, similar to ``dtypes``, but indicates
  if the underlying is sparse/dense (as well as the dtype)
- All ``NDFrame`` objects can now use ``__finalize__()`` to specify various
  values to propagate to new objects from an existing one (e.g. ``name`` in ``Series`` will
  follow more automatically now)
- Internal type checking is now done via a suite of generated classes, allowing ``isinstance(value, klass)``
  without having to directly import the klass, courtesy of @jtratner
- Bug in Series update where the parent frame is not updating its cache based on
  changes (:issue:`4080`) or types (:issue:`3217`), fillna (:issue:`3386`)
- Indexing with dtype conversions fixed (:issue:`4463`, :issue:`4204`)
- Refactor ``Series.reindex`` to core/generic.py (:issue:`4604`, :issue:`4618`), allow ``method=`` in reindexing
  on a Series to work
- ``Series.copy`` no longer accepts the ``order`` parameter and is now consistent with ``NDFrame`` copy
- Refactor ``rename`` methods to core/generic.py; fixes ``Series.rename`` for (:issue:`4605`), and adds ``rename``
  with the same signature for ``Panel``
- Refactor ``clip`` methods to core/generic.py (:issue:`4798`)
- Refactor of ``_get_numeric_data/_get_bool_data`` to core/generic.py, allowing Series/Panel functionality
- ``Series`` (for index) / ``Panel`` (for items) now allow attribute access to its elements  (:issue:`1903`)

  .. ipython:: python

     s = pd.Series([1, 2, 3], index=list('abc'))
     s.b
     s.a = 5
     s

.. _release.bug_fixes-0.13.0:

Bug fixes
~~~~~~~~~

- ``HDFStore``

  - raising an invalid ``TypeError`` rather than ``ValueError`` when
    appending with a different block ordering (:issue:`4096`)
  - ``read_hdf`` was not respecting as passed ``mode`` (:issue:`4504`)
  - appending a 0-len table will work correctly (:issue:`4273`)
  - ``to_hdf`` was raising when passing both arguments ``append`` and
    ``table`` (:issue:`4584`)
  - reading from a store with duplicate columns across dtypes would raise
    (:issue:`4767`)
  - Fixed a bug where ``ValueError`` wasn't correctly raised when column
    names weren't strings (:issue:`4956`)
  - A zero length series written in Fixed format not deserializing properly.
    (:issue:`4708`)
  - Fixed decoding perf issue on pyt3 (:issue:`5441`)
  - Validate levels in a MultiIndex before storing (:issue:`5527`)
  - Correctly handle ``data_columns`` with a Panel (:issue:`5717`)
- Fixed bug in tslib.tz_convert(vals, tz1, tz2): it could raise IndexError
  exception while trying to access trans[pos + 1] (:issue:`4496`)
- The ``by`` argument now works correctly with the ``layout`` argument
  (:issue:`4102`, :issue:`4014`) in ``*.hist`` plotting methods
- Fixed bug in ``PeriodIndex.map`` where using ``str`` would return the str
  representation of the index (:issue:`4136`)
- Fixed test failure ``test_time_series_plot_color_with_empty_kwargs`` when
  using custom matplotlib default colors (:issue:`4345`)
- Fix running of stata IO tests. Now uses temporary files to write
  (:issue:`4353`)
- Fixed an issue where ``DataFrame.sum`` was slower than ``DataFrame.mean``
  for integer valued frames (:issue:`4365`)
- ``read_html`` tests now work with Python 2.6 (:issue:`4351`)
- Fixed bug where ``network`` testing was throwing ``NameError`` because a
  local variable was undefined (:issue:`4381`)
- In ``to_json``, raise if a passed ``orient`` would cause loss of data
  because of a duplicate index (:issue:`4359`)
- In ``to_json``, fix date handling so milliseconds are the default timestamp
  as the docstring says (:issue:`4362`).
- ``as_index`` is no longer ignored when doing groupby apply (:issue:`4648`,
  :issue:`3417`)
- JSON NaT handling fixed, NaTs are now serialized to `null` (:issue:`4498`)
- Fixed JSON handling of escapable characters in JSON object keys
  (:issue:`4593`)
- Fixed passing ``keep_default_na=False`` when ``na_values=None``
  (:issue:`4318`)
- Fixed bug with ``values`` raising an error on a DataFrame with duplicate
  columns and mixed dtypes, surfaced in (:issue:`4377`)
- Fixed bug with duplicate columns and type conversion in ``read_json`` when
  ``orient='split'`` (:issue:`4377`)
- Fixed JSON bug where locales with decimal separators other than '.' threw
  exceptions when encoding / decoding certain values. (:issue:`4918`)
- Fix ``.iat`` indexing with a ``PeriodIndex`` (:issue:`4390`)
- Fixed an issue where ``PeriodIndex`` joining with self was returning a new
  instance rather than the same instance (:issue:`4379`); also adds a test
  for this for the other index types
- Fixed a bug with all the dtypes being converted to object when using the
  CSV cparser with the usecols parameter (:issue:`3192`)
- Fix an issue in merging blocks where the resulting DataFrame had partially
  set _ref_locs (:issue:`4403`)
- Fixed an issue where hist subplots were being overwritten when they were
  called using the top level matplotlib API (:issue:`4408`)
- Fixed a bug where calling ``Series.astype(str)`` would truncate the string
  (:issue:`4405`, :issue:`4437`)
- Fixed a py3 compat issue where bytes were being repr'd as tuples
  (:issue:`4455`)
- Fixed Panel attribute naming conflict if item is named 'a'
  (:issue:`3440`)
- Fixed an issue where duplicate indexes were raising when plotting
  (:issue:`4486`)
- Fixed an issue where cumsum and cumprod didn't work with bool dtypes
  (:issue:`4170`, :issue:`4440`)
- Fixed Panel slicing issued in ``xs`` that was returning an incorrect dimmed
  object (:issue:`4016`)
- Fix resampling bug where custom reduce function not used if only one group
  (:issue:`3849`, :issue:`4494`)
- Fixed Panel assignment with a transposed frame (:issue:`3830`)
- Raise on set indexing with a Panel and a Panel as a value which needs
  alignment (:issue:`3777`)
- frozenset objects now raise in the ``Series`` constructor (:issue:`4482`,
  :issue:`4480`)
- Fixed issue with sorting a duplicate MultiIndex that has multiple dtypes
  (:issue:`4516`)
- Fixed bug in ``DataFrame.set_values`` which was causing name attributes to
  be lost when expanding the index. (:issue:`3742`, :issue:`4039`)
- Fixed issue where individual ``names``, ``levels`` and ``labels`` could be
  set on ``MultiIndex`` without validation (:issue:`3714`, :issue:`4039`)
- Fixed (:issue:`3334`) in pivot_table. Margins did not compute if values is
  the index.
- Fix bug in having a rhs of ``np.timedelta64`` or ``np.offsets.DateOffset``
  when operating with datetimes (:issue:`4532`)
- Fix arithmetic with series/datetimeindex and ``np.timedelta64`` not working
  the same (:issue:`4134`) and buggy timedelta in NumPy 1.6 (:issue:`4135`)
- Fix bug in ``pd.read_clipboard`` on windows with PY3 (:issue:`4561`); not
  decoding properly
- ``tslib.get_period_field()`` and ``tslib.get_period_field_arr()`` now raise
  if code argument out of range (:issue:`4519`, :issue:`4520`)
- Fix boolean indexing on an empty series loses index names (:issue:`4235`),
  infer_dtype works with empty arrays.
- Fix reindexing with multiple axes; if an axes match was not replacing the
  current axes, leading to a possible lazy frequency inference issue
  (:issue:`3317`)
- Fixed issue where ``DataFrame.apply`` was reraising exceptions incorrectly
  (causing the original stack trace to be truncated).
- Fix selection with ``ix/loc`` and non_unique selectors (:issue:`4619`)
- Fix assignment with iloc/loc involving a dtype change in an existing column
  (:issue:`4312`, :issue:`5702`) have internal setitem_with_indexer in core/indexing
  to use Block.setitem
- Fixed bug where thousands operator was not handled correctly for floating
  point numbers in csv_import (:issue:`4322`)
- Fix an issue with CacheableOffset not properly being used by many
  DateOffset; this prevented the DateOffset from being cached (:issue:`4609`)
- Fix boolean comparison with a DataFrame on the lhs, and a list/tuple on the
  rhs (:issue:`4576`)
- Fix error/dtype conversion with setitem of ``None`` on ``Series/DataFrame``
  (:issue:`4667`)
- Fix decoding based on a passed in non-default encoding in ``pd.read_stata``
  (:issue:`4626`)
- Fix ``DataFrame.from_records`` with a plain-vanilla ``ndarray``.
  (:issue:`4727`)
- Fix some inconsistencies with ``Index.rename`` and ``MultiIndex.rename``,
  etc. (:issue:`4718`, :issue:`4628`)
- Bug in using ``iloc/loc`` with a cross-sectional and duplicate indices
  (:issue:`4726`)
- Bug with using ``QUOTE_NONE`` with ``to_csv`` causing ``Exception``.
  (:issue:`4328`)
- Bug with Series indexing not raising an error when the right-hand-side has
  an incorrect length (:issue:`2702`)
- Bug in MultiIndexing with a partial string selection as one part of a
  MultIndex (:issue:`4758`)
- Bug with reindexing on the index with a non-unique index will now raise
  ``ValueError`` (:issue:`4746`)
- Bug in setting with ``loc/ix`` a single indexer with a MultiIndex axis and
  a NumPy array, related to (:issue:`3777`)
- Bug in concatenation with duplicate columns across dtypes not merging with
  axis=0 (:issue:`4771`, :issue:`4975`)
- Bug in ``iloc`` with a slice index failing (:issue:`4771`)
- Incorrect error message with no colspecs or width in ``read_fwf``.
  (:issue:`4774`)
- Fix bugs in indexing in a Series with a duplicate index (:issue:`4548`,
  :issue:`4550`)
- Fixed bug with reading compressed files with ``read_fwf`` in Python 3.
  (:issue:`3963`)
- Fixed an issue with a duplicate index and assignment with a dtype change
  (:issue:`4686`)
- Fixed bug with reading compressed files in as ``bytes`` rather than ``str``
  in Python 3. Simplifies bytes-producing file-handling in Python 3
  (:issue:`3963`, :issue:`4785`).
- Fixed an issue related to ticklocs/ticklabels with log scale bar plots
  across different versions of matplotlib (:issue:`4789`)
- Suppressed DeprecationWarning associated with internal calls issued by
  repr() (:issue:`4391`)
- Fixed an issue with a duplicate index and duplicate selector with ``.loc``
  (:issue:`4825`)
- Fixed an issue with ``DataFrame.sort_index`` where, when sorting by a
  single column and passing a list for ``ascending``, the argument for
  ``ascending`` was being interpreted as ``True`` (:issue:`4839`,
  :issue:`4846`)
- Fixed ``Panel.tshift`` not working. Added `freq` support to ``Panel.shift``
  (:issue:`4853`)
- Fix an issue in TextFileReader w/ Python engine (i.e. PythonParser)
  with thousands != "," (:issue:`4596`)
- Bug in getitem with a duplicate index when using where (:issue:`4879`)
- Fix Type inference code coerces float column into datetime (:issue:`4601`)
- Fixed ``_ensure_numeric`` does not check for complex numbers
  (:issue:`4902`)
- Fixed a bug in ``Series.hist`` where two figures were being created when
  the ``by`` argument was passed (:issue:`4112`, :issue:`4113`).
- Fixed a bug in ``convert_objects`` for > 2 ndims (:issue:`4937`)
- Fixed a bug in DataFrame/Panel cache insertion and subsequent indexing
  (:issue:`4939`, :issue:`5424`)
- Fixed string methods for ``FrozenNDArray`` and ``FrozenList``
  (:issue:`4929`)
- Fixed a bug with setting invalid or out-of-range values in indexing
  enlargement scenarios (:issue:`4940`)
- Tests for fillna on empty Series (:issue:`4346`), thanks @immerrr
- Fixed ``copy()`` to shallow copy axes/indices as well and thereby keep
  separate metadata. (:issue:`4202`, :issue:`4830`)
- Fixed skiprows option in Python parser for read_csv (:issue:`4382`)
- Fixed bug preventing ``cut`` from working with ``np.inf`` levels without
  explicitly passing labels (:issue:`3415`)
- Fixed wrong check for overlapping in ``DatetimeIndex.union``
  (:issue:`4564`)
- Fixed conflict between thousands separator and date parser in csv_parser
  (:issue:`4678`)
- Fix appending when dtypes are not the same (error showing mixing
  float/np.datetime64) (:issue:`4993`)
- Fix repr for DateOffset. No longer show duplicate entries in kwds.
  Removed unused offset fields. (:issue:`4638`)
- Fixed wrong index name during read_csv if using usecols. Applies to c
  parser only. (:issue:`4201`)
- ``Timestamp`` objects can now appear in the left hand side of a comparison
  operation with a ``Series`` or ``DataFrame`` object (:issue:`4982`).
- Fix a bug when indexing with ``np.nan`` via ``iloc/loc`` (:issue:`5016`)
- Fixed a bug where low memory c parser could create different types in
  different chunks of the same file. Now coerces to numerical type or raises
  warning. (:issue:`3866`)
- Fix a bug where reshaping a ``Series`` to its own shape raised
  ``TypeError`` (:issue:`4554`) and other reshaping issues.
- Bug in setting with ``ix/loc`` and a mixed int/string index (:issue:`4544`)
- Make sure series-series boolean comparisons are label based (:issue:`4947`)
- Bug in multi-level indexing with a Timestamp partial indexer
  (:issue:`4294`)
- Tests/fix for MultiIndex construction of an all-nan frame (:issue:`4078`)
- Fixed a bug where :func:`~pandas.read_html` wasn't correctly inferring
  values of tables with commas (:issue:`5029`)
- Fixed a bug where :func:`~pandas.read_html` wasn't providing a stable
  ordering of returned tables (:issue:`4770`, :issue:`5029`).
- Fixed a bug where :func:`~pandas.read_html` was incorrectly parsing when
  passed ``index_col=0`` (:issue:`5066`).
- Fixed a bug where :func:`~pandas.read_html` was incorrectly inferring the
  type of headers (:issue:`5048`).
- Fixed a bug where ``DatetimeIndex`` joins with ``PeriodIndex`` caused a
  stack overflow (:issue:`3899`).
- Fixed a bug where ``groupby`` objects didn't allow plots (:issue:`5102`).
- Fixed a bug where ``groupby`` objects weren't tab-completing column names
  (:issue:`5102`).
- Fixed a bug where ``groupby.plot()`` and friends were duplicating figures
  multiple times (:issue:`5102`).
- Provide automatic conversion of ``object`` dtypes on fillna, related
  (:issue:`5103`)
- Fixed a bug where default options were being overwritten in the option
  parser cleaning (:issue:`5121`).
- Treat a list/ndarray identically for ``iloc`` indexing with list-like
  (:issue:`5006`)
- Fix ``MultiIndex.get_level_values()`` with missing values (:issue:`5074`)
- Fix bound checking for Timestamp() with datetime64 input (:issue:`4065`)
- Fix a bug where ``TestReadHtml`` wasn't calling the correct ``read_html()``
  function (:issue:`5150`).
- Fix a bug with ``NDFrame.replace()`` which made replacement appear as
  though it was (incorrectly) using regular expressions (:issue:`5143`).
- Fix better error message for to_datetime (:issue:`4928`)
- Made sure different locales are tested on travis-ci (:issue:`4918`). Also
  adds a couple of utilities for getting locales and setting locales with a
  context manager.
- Fixed segfault on ``isnull(MultiIndex)`` (now raises an error instead)
  (:issue:`5123`, :issue:`5125`)
- Allow duplicate indices when performing operations that align
  (:issue:`5185`, :issue:`5639`)
- Compound dtypes in a constructor raise ``NotImplementedError``
  (:issue:`5191`)
- Bug in comparing duplicate frames (:issue:`4421`) related
- Bug in describe on duplicate frames
- Bug in ``to_datetime`` with a format and ``coerce=True`` not raising
  (:issue:`5195`)
- Bug in ``loc`` setting with multiple indexers and a rhs of a Series that
  needs broadcasting (:issue:`5206`)
- Fixed bug where inplace setting of levels or labels on ``MultiIndex`` would
  not clear cached ``values`` property and therefore return wrong ``values``.
  (:issue:`5215`)
- Fixed bug where filtering a grouped DataFrame or Series did not maintain
  the original ordering (:issue:`4621`).
- Fixed ``Period`` with a business date freq to always roll-forward if on a
  non-business date. (:issue:`5203`)
- Fixed bug in Excel writers where frames with duplicate column names weren't
  written correctly. (:issue:`5235`)
- Fixed issue with ``drop`` and a non-unique index on Series (:issue:`5248`)
- Fixed segfault in C parser caused by passing more names than columns in
  the file. (:issue:`5156`)
- Fix ``Series.isin`` with date/time-like dtypes (:issue:`5021`)
- C and Python Parser can now handle the more common MultiIndex column
  format which doesn't have a row for index names (:issue:`4702`)
- Bug when trying to use an out-of-bounds date as an object dtype
  (:issue:`5312`)
- Bug when trying to display an embedded PandasObject (:issue:`5324`)
- Allows operating of Timestamps to return a datetime if the result is out-of-bounds
  related (:issue:`5312`)
- Fix return value/type signature of ``initObjToJSON()`` to be compatible
  with numpy's ``import_array()`` (:issue:`5334`, :issue:`5326`)
- Bug when renaming then set_index on a DataFrame (:issue:`5344`)
- Test suite no longer leaves around temporary files when testing graphics. (:issue:`5347`)
  (thanks for catching this @yarikoptic!)
- Fixed html tests on win32. (:issue:`4580`)
- Make sure that ``head/tail`` are ``iloc`` based, (:issue:`5370`)
- Fixed bug for ``PeriodIndex`` string representation if there are 1 or 2
  elements. (:issue:`5372`)
- The GroupBy methods ``transform`` and ``filter`` can be used on Series
  and DataFrames that have repeated (non-unique) indices. (:issue:`4620`)
- Fix empty series not printing name in repr (:issue:`4651`)
- Make tests create temp files in temp directory by default. (:issue:`5419`)
- ``pd.to_timedelta`` of a scalar returns a scalar (:issue:`5410`)
- ``pd.to_timedelta`` accepts ``NaN`` and ``NaT``, returning ``NaT`` instead of raising (:issue:`5437`)
- performance improvements in ``isnull`` on larger size pandas objects
- Fixed various setitem with 1d ndarray that does not have a matching
  length to the indexer (:issue:`5508`)
- Bug in getitem with a MultiIndex and ``iloc`` (:issue:`5528`)
- Bug in delitem on a Series (:issue:`5542`)
- Bug fix in apply when using custom function and objects are not mutated (:issue:`5545`)
- Bug in selecting from a non-unique index with ``loc`` (:issue:`5553`)
- Bug in groupby returning non-consistent types when user function returns a ``None``, (:issue:`5592`)
- Work around regression in numpy 1.7.0 which erroneously raises IndexError from ``ndarray.item`` (:issue:`5666`)
- Bug in repeated indexing of object with resultant non-unique index (:issue:`5678`)
- Bug in fillna with Series and a passed series/dict (:issue:`5703`)
- Bug in groupby transform with a datetime-like grouper (:issue:`5712`)
- Bug in MultiIndex selection in PY3 when using certain keys (:issue:`5725`)
- Row-wise concat of differing dtypes failing in certain cases (:issue:`5754`)

.. _whatsnew_0.13.0.contributors:

Contributors
~~~~~~~~~~~~

.. contributors:: v0.12.0..v0.13.0
