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# Version 0.5.0 (October 24, 2011)

## New features

- Added `DataFrame.align` method with standard join options

- Added `parse_dates` option to `read_csv` and `read_table` methods to optionally try to parse dates in the index columns

- Added `nrows`, `chunksize`, and `iterator` arguments to `read_csv` and `read_table`. The last two return a new `TextParser` class capable of lazily iterating through chunks of a flat file (GH 242)

- Added ability to join on multiple columns in `DataFrame.join` (GH 214)

- Added private `_get_duplicates` function to `Index` for identifying duplicate values more easily (ENH5c)

- Added column attribute access to DataFrame.

- Added Python tab completion hook for DataFrame columns. (GH 233, GH 230)

- Implemented `Series.describe` for Series containing objects (GH 241)

- Added inner join option to `DataFrame.join` when joining on key(s) (GH 248)

- Implemented selecting DataFrame columns by passing a list to `__getitem__` (GH 253)

- Implemented & and | to intersect / union Index objects, respectively (GH 261)

- Added `pivot_table` convenience function to pandas namespace (GH 234)

- Implemented `Panel.rename_axis` function (GH 243)

- DataFrame will show index level names in console output (GH 334)

- Implemented `Panel.take`

- Added `set_eng_float_format` for alternate DataFrame floating point string formatting (ENH61)

- Added convenience `set_index` function for creating a DataFrame index from its existing columns

- Implemented `groupby` hierarchical index level name (GH 223)

- Added support for different delimiters in `DataFrame.to_csv` (GH 244)

## Performance enhancements

- VBENCH Major performance improvements in file parsing functions `read_csv` and `read_table`

- VBENCH Added Cython function for converting tuples to ndarray very fast. Speeds up many MultiIndex-related operations

- VBENCH Refactored merging / joining code into a tidy class and disabled unnecessary computations in the float/object case, thus getting about 10% better performance (GH 211)

- VBENCH Improved speed of `DataFrame.xs` on mixed-type DataFrame objects by about 5x, regression from 0.3.0 (GH 215)

- VBENCH With new `DataFrame.align` method, speeding up binary operations between differently-indexed DataFrame objects by 10-25%.

- VBENCH Significantly sped up conversion of nested dict into DataFrame (GH 212)

- VBENCH Significantly speed up DataFrame `__repr__` and `count` on large mixed-type DataFrame objects

## Contributors

A total of 9 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.

- Aman Thakral +

- Luca Beltrame +

- Nick Pentreath +

- Skipper Seabold

- Thomas Kluyver +

- Wes McKinney

- Yaroslav Halchenko +

- lodagro +

- unknown +