v.0.4.1 through v0.4.3 (September 25 - October 9, 2011)

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`)

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

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