Version 0.15.2 (December 12, 2014)

- Indexing in ``MultiIndex`` beyond lex-sort depth is now supported, though
  a lexically sorted index will have a better performance. (:issue:`2646`)

  .. code-block:: ipython

    In [1]: df = pd.DataFrame({'jim':[0, 0, 1, 1],
       ...:                    'joe':['x', 'x', 'z', 'y'],
       ...:                    'jolie':np.random.rand(4)}).set_index(['jim', 'joe'])
       ...:

    In [2]: df
    Out[2]:
                jolie
    jim joe
    0   x    0.126970
        x    0.966718
    1   z    0.260476
        y    0.897237

    [4 rows x 1 columns]

    In [3]: df.index.lexsort_depth
    Out[3]: 1

    # in prior versions this would raise a KeyError
    # will now show a PerformanceWarning
    In [4]: df.loc[(1, 'z')]
    Out[4]:
                jolie
    jim joe
    1   z    0.260476

    [1 rows x 1 columns]

    # lexically sorting
    In [5]: df2 = df.sort_index()

    In [6]: df2
    Out[6]:
                jolie
    jim joe
    0   x    0.126970
        x    0.966718
    1   y    0.897237
        z    0.260476

    [4 rows x 1 columns]

    In [7]: df2.index.lexsort_depth
    Out[7]: 2

    In [8]: df2.loc[(1,'z')]
    Out[8]:
                jolie
    jim joe
    1   z    0.260476

    [1 rows x 1 columns]

- Bug in unique of Series with ``category`` dtype, which returned all categories regardless
  whether they were "used" or not (see :issue:`8559` for the discussion).
  Previous behaviour was to return all categories:

  .. code-block:: ipython

    In [3]: cat = pd.Categorical(['a', 'b', 'a'], categories=['a', 'b', 'c'])

    In [4]: cat
    Out[4]:
    [a, b, a]
    Categories (3, object): [a < b < c]

    In [5]: cat.unique()
    Out[5]: array(['a', 'b', 'c'], dtype=object)

  Now, only the categories that do effectively occur in the array are returned:

  .. ipython:: python

    cat = pd.Categorical(['a', 'b', 'a'], categories=['a', 'b', 'c'])
    cat.unique()

- ``Series.all`` and ``Series.any`` now support the ``level`` and ``skipna`` parameters. ``Series.all``, ``Series.any``, ``Index.all``, and ``Index.any`` no longer support the ``out`` and ``keepdims`` parameters, which existed for compatibility with ndarray. Various index types no longer support the ``all`` and ``any`` aggregation functions and will now raise ``TypeError``. (:issue:`8302`).

- Allow equality comparisons of Series with a categorical dtype and object dtype; previously these would raise ``TypeError`` (:issue:`8938`)

- Bug in ``NDFrame``: conflicting attribute/column names now behave consistently between getting and setting. Previously, when both a column and attribute named ``y`` existed, ``data.y`` would return the attribute, while ``data.y = z`` would update the column (:issue:`8994`)

  .. ipython:: python

     data = pd.DataFrame({'x': [1, 2, 3]})
     data.y = 2
     data['y'] = [2, 4, 6]
     data

     # this assignment was inconsistent
     data.y = 5

  Old behavior:

  .. code-block:: ipython

     In [6]: data.y
     Out[6]: 2

     In [7]: data['y'].values
     Out[7]: array([5, 5, 5])

  New behavior:

  .. ipython:: python

     data.y
     data['y'].values

- ``Timestamp('now')`` is now equivalent to ``Timestamp.now()`` in that it returns the local time rather than UTC. Also, ``Timestamp('today')`` is now equivalent to ``Timestamp.today()`` and both have ``tz`` as a possible argument. (:issue:`9000`)

- Fix negative step support for label-based slices (:issue:`8753`)

  Old behavior:

  .. code-block:: ipython

     In [1]: s = pd.Series(np.arange(3), ['a', 'b', 'c'])
     Out[1]:
     a    0
     b    1
     c    2
     dtype: int64

     In [2]: s.loc['c':'a':-1]
     Out[2]:
     c    2
     dtype: int64

  New behavior:

  .. ipython:: python

     s = pd.Series(np.arange(3), ['a', 'b', 'c'])
     s.loc['c':'a':-1]


.. _whatsnew_0152.enhancements:

Enhancements

- Reduce memory usage when skiprows is an integer in read_csv (:issue:`8681`)
- Performance boost for ``to_datetime`` conversions with a passed ``format=``, and the ``exact=False`` (:issue:`8904`)


.. _whatsnew_0152.bug_fixes:

Bug fixes
~~~~~~~~~

- Bug in concat of Series with ``category`` dtype which were coercing to ``object``. (:issue:`8641`)
- Bug in Timestamp-Timestamp not returning a Timedelta type and datelike-datelike ops with timezones (:issue:`8865`)
- Made consistent a timezone mismatch exception (either tz operated with None or incompatible timezone), will now return ``TypeError`` rather than ``ValueError`` (a couple of edge cases only), (:issue:`8865`)
- Bug in using a ``pd.Grouper(key=...)`` with no level/axis or level only (:issue:`8795`, :issue:`8866`)
- Report a ``TypeError`` when invalid/no parameters are passed in a groupby (:issue:`8015`)
- Bug in packaging pandas with ``py2app/cx_Freeze`` (:issue:`8602`, :issue:`8831`)
- Bug in ``groupby`` signatures that didn't include \*args or \*\*kwargs (:issue:`8733`).
- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo and when it receives no data from Yahoo (:issue:`8761`), (:issue:`8783`).
- Unclear error message in csv parsing when passing dtype and names and the parsed data is a different data type (:issue:`8833`)
- Bug in slicing a MultiIndex with an empty list and at least one boolean indexer (:issue:`8781`)
- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo (:issue:`8761`).
- ``Timedelta`` kwargs may now be numpy ints and floats (:issue:`8757`).
- Fixed several outstanding bugs for ``Timedelta`` arithmetic and comparisons (:issue:`8813`, :issue:`5963`, :issue:`5436`).
- ``sql_schema`` now generates dialect appropriate ``CREATE TABLE`` statements (:issue:`8697`)
- ``slice`` string method now takes step into account (:issue:`8754`)
- Bug in ``BlockManager`` where setting values with different type would break block integrity (:issue:`8850`)
- Bug in ``DatetimeIndex`` when using ``time`` object as key (:issue:`8667`)
- Bug in ``merge`` where ``how='left'`` and ``sort=False`` would not preserve left frame order (:issue:`7331`)
- Bug in ``MultiIndex.reindex`` where reindexing at level would not reorder labels (:issue:`4088`)
- Bug in certain operations with dateutil timezones, manifesting with dateutil 2.3 (:issue:`8639`)
- Regression in DatetimeIndex iteration with a Fixed/Local offset timezone (:issue:`8890`)
- Bug in ``to_datetime`` when parsing a nanoseconds using the ``%f`` format (:issue:`8989`)
- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo and when it receives no data from Yahoo (:issue:`8761`), (:issue:`8783`).
- Fix: The font size was only set on x axis if vertical or the y axis if horizontal. (:issue:`8765`)
- Fixed division by 0 when reading big csv files in python 3 (:issue:`8621`)
- Bug in outputting a MultiIndex with ``to_html,index=False`` which would add an extra column (:issue:`8452`)
- Imported categorical variables from Stata files retain the ordinal information in the underlying data (:issue:`8836`).
- Defined ``.size`` attribute across ``NDFrame`` objects to provide compat with numpy >= 1.9.1; buggy with ``np.array_split`` (:issue:`8846`)
- Skip testing of histogram plots for matplotlib <= 1.2 (:issue:`8648`).
- Bug where ``get_data_google`` returned object dtypes (:issue:`3995`)
- Bug in ``DataFrame.stack(..., dropna=False)`` when the DataFrame's ``columns`` is a ``MultiIndex``
  whose ``labels`` do not reference all its ``levels``. (:issue:`8844`)
- Bug in that Option context applied on ``__enter__`` (:issue:`8514`)
- Bug in resample that causes a ValueError when resampling across multiple days
  and the last offset is not calculated from the start of the range (:issue:`8683`)
- Bug where ``DataFrame.plot(kind='scatter')`` fails when checking if an np.array is in the DataFrame (:issue:`8852`)
- Bug in ``pd.infer_freq/DataFrame.inferred_freq`` that prevented proper sub-daily frequency inference when the index contained DST days (:issue:`8772`).
- Bug where index name was still used when plotting a series with ``use_index=False`` (:issue:`8558`).
- Bugs when trying to stack multiple columns, when some (or all) of the level names are numbers (:issue:`8584`).
- Bug in ``MultiIndex`` where ``__contains__`` returns wrong result if index is not lexically sorted or unique (:issue:`7724`)
- BUG CSV: fix problem with trailing white space in skipped rows, (:issue:`8679`), (:issue:`8661`), (:issue:`8983`)
- Regression in ``Timestamp`` does not parse 'Z' zone designator for UTC (:issue:`8771`)
- Bug in ``StataWriter`` the produces writes strings with 244 characters irrespective of actual size (:issue:`8969`)
- Fixed ValueError raised by cummin/cummax when datetime64 Series contains NaT. (:issue:`8965`)
- Bug in DataReader returns object dtype if there are missing values (:issue:`8980`)
- Bug in plotting if sharex was enabled and index was a timeseries, would show labels on multiple axes (:issue:`3964`).
- Bug where passing a unit to the TimedeltaIndex constructor applied the to nano-second conversion twice. (:issue:`9011`).
- Bug in plotting of a period-like array (:issue:`9012`)


.. _whatsnew_0.15.2.contributors:

Contributors