.. _whatsnew_04x:

Versions 0.4.1 through 0.4.3 (September 25 - October 9, 2011)
-------------------------------------------------------------

{{ header }}

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

- Added Python 3 support using 2to3 (:issue:`200`)
- :ref:`Added <dsintro.name_attribute>` ``name`` attribute to ``Series``, now
  prints as part of ``Series.__repr__``
- :ref:`Added <missing.isna>` instance methods ``isnull`` and ``notnull`` to
  Series (:issue:`209`, :issue:`203`)
- :ref:`Added <basics.align>` ``Series.align`` method for aligning two series
  with choice of join method (ENH56_)
- :ref:`Added <advanced.get_level_values>` method ``get_level_values`` to
  ``MultiIndex`` (:issue:`188`)
- Set values in mixed-type ``DataFrame`` objects via ``.ix`` indexing attribute (:issue:`135`)
- Added new ``DataFrame`` :ref:`methods <basics.dtypes>`
  ``get_dtype_counts`` and property ``dtypes`` (ENHdc_)
- Added :ref:`ignore_index <merging.ignore_index>` option to
  ``DataFrame.append`` to stack DataFrames (ENH1b_)
- ``read_csv`` tries to :ref:`sniff <io.sniff>` delimiters using
  ``csv.Sniffer`` (:issue:`146`)
- ``read_csv`` can :ref:`read <io.csv_multiindex>` multiple columns into a
  ``MultiIndex``; DataFrame's ``to_csv`` method writes out a corresponding
  ``MultiIndex`` (:issue:`151`)
- ``DataFrame.rename`` has a new ``copy`` parameter to :ref:`rename
  <basics.rename>` a DataFrame in place (ENHed_)
- :ref:`Enable <reshaping.unstack_by_name>` unstacking by name (:issue:`142`)
- :ref:`Enable <advanced.sortlevel_byname>` ``sortlevel`` to work by level (:issue:`141`)

Performance enhancements
~~~~~~~~~~~~~~~~~~~~~~~~

- Altered binary operations on differently-indexed SparseSeries objects
  to use the integer-based (dense) alignment logic which is faster with a
  larger number of blocks (:issue:`205`)
- Wrote faster Cython data alignment / merging routines resulting in
  substantial speed increases
- Improved performance of ``isnull`` and ``notnull``, a regression from v0.3.0
  (:issue:`187`)
- Refactored code related to ``DataFrame.join`` so that intermediate aligned
  copies of the data in each ``DataFrame`` argument do not need to be created.
  Substantial performance increases result (:issue:`176`)
- Substantially improved performance of generic ``Index.intersection`` and
  ``Index.union``
- Implemented ``BlockManager.take`` resulting in significantly faster ``take``
  performance on mixed-type ``DataFrame`` objects (:issue:`104`)
- Improved performance of ``Series.sort_index``
- Significant groupby performance enhancement: removed unnecessary integrity
  checks in DataFrame internals that were slowing down slicing operations to
  retrieve groups
- Optimized ``_ensure_index`` function resulting in performance savings in
  type-checking Index objects
- Wrote fast time series merging / joining methods in Cython. Will be
  integrated later into DataFrame.join and related functions

.. _ENH1b: https://github.com/pandas-dev/pandas/commit/1ba56251f0013ff7cd8834e9486cef2b10098371
.. _ENHdc: https://github.com/pandas-dev/pandas/commit/dca3c5c5a6a3769ee01465baca04cfdfa66a4f76
.. _ENHed: https://github.com/pandas-dev/pandas/commit/edd9f1945fc010a57fa0ae3b3444d1fffe592591
.. _ENH56: https://github.com/pandas-dev/pandas/commit/56e0c9ffafac79ce262b55a6a13e1b10a88fbe93

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

.. contributors:: v0.4.1..v0.4.3
