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Release Notes

This is the list of changes to pandas between each release. For full details, see the commit logs at

What is it

pandas is a Python package providing fast, flexible, and expressive data structures designed to make working with “relational” or “labeled” data both easy and intuitive. It aims to be the fundamental high-level building block for doing practical, real world data analysis in Python. Additionally, it has the broader goal of becoming the most powerful and flexible open source data analysis / manipulation tool available in any language.

Where to get it

pandas 0.9.1

Release date: NOT YET RELEASED

Improvements to existing features

  • Improve HTML display of DataFrame objects with hierarchical columns

pandas 0.9.0

Release date: 10/7/2012

New features

  • Add str.encode and str.decode to Series (#1706)
  • Add to_latex method to DataFrame (#1735)
  • Add convenient expanding window equivalents of all rolling_* ops (#1785)
  • Add Options class to for fetching options data from Yahoo! Finance (#1748, #1739)
  • Recognize and convert more boolean values in file parsing (Yes, No, TRUE, FALSE, variants thereof) (#1691, #1295)
  • Add Panel.update method, analogous to DataFrame.update (#1999, #1988)

Improvements to existing features

  • Proper handling of NA values in merge operations (#1990)
  • Add flags option for re.compile in some Series.str methods (#1659)
  • Parsing of UTC date strings in read_* functions (#1693)
  • Handle generator input to Series (#1679)
  • Add na_action='ignore' to to quietly propagate NAs (#1661)
  • Add args/kwds options to Series.apply (#1829)
  • Add inplace option to Series/DataFrame.reset_index (#1797)
  • Add level parameter to Series.reset_index
  • Add quoting option for DataFrame.to_csv (#1902)
  • Indicate long column value truncation in DataFrame output with ... (#1854)
  • will not do data alignment, and also work with Series (#1915)
  • Add na option for missing data handling in some vectorized string methods (#1689)
  • If index_label=False in DataFrame.to_csv, do not print fields/commas in the text output. Results in easier importing into R (#1583)
  • Can pass tuple/list of axes to DataFrame.dropna to simplify repeated calls (dropping both columns and rows) (#924)
  • Improve DataFrame.to_html output for hierarchically-indexed rows (do not repeat levels) (#1929)
  • TimeSeries.between_time can now select times across midnight (#1871)
  • Enable skip_footer parameter in ExcelFile.parse (#1843)

API Changes

  • Change default header names in read_* functions to more Pythonic X0, X1, etc. instead of X.1, X.2. (#2000)
  • Deprecated day_of_year API removed from PeriodIndex, use dayofyear (#1723)
  • Don't modify NumPy suppress printoption at import time
  • The internal HDF5 data arrangement for DataFrames has been transposed. Legacy files will still be readable by HDFStore (#1834, #1824)
  • Legacy cruft removed: pandas.stats.misc.quantileTS
  • Use ISO8601 format for Period repr: monthly, daily, and on down (#1776)
  • Empty DataFrame columns are now created as object dtype. This will prevent a class of TypeErrors that was occurring in code where the dtype of a column would depend on the presence of data or not (e.g. a SQL query having results) (#1783)
  • Setting parts of DataFrame/Panel using ix now aligns input Series/DataFrame (#1630)
  • first and last methods in GroupBy no longer drop non-numeric columns (#1809)
  • Resolved inconsistencies in specifying custom NA values in text parser. na_values of type dict no longer override default NAs unless keep_default_na is set to false explicitly (#1657)
  • Enable skipfooter parameter in text parsers as an alias for skip_footer

Bug fixes

  • Perform arithmetic column-by-column in mixed-type DataFrame to avoid type upcasting issues. Caused downstream DataFrame.diff bug (#1896)
  • Fix matplotlib auto-color assignment when no custom spectrum passed. Also respect passed color keyword argument (#1711)
  • Fix resampling logical error with closed='left' (#1726)
  • Fix critical DatetimeIndex.union bugs (#1730, #1719, #1745, #1702, #1753)
  • Fix critical DatetimeIndex.intersection bug with unanchored offsets (#1708)
  • Fix MM-YYYY time series indexing case (#1672)
  • Fix case where Categorical group key was not being passed into index in GroupBy result (#1701)
  • Handle Ellipsis in Series.__getitem__/__setitem__ (#1721)
  • Fix some bugs with handling datetime64 scalars of other units in NumPy 1.6 and 1.7 (#1717)
  • Fix performance issue in MultiIndex.format (#1746)
  • Fixed GroupBy bugs interacting with DatetimeIndex asof / map methods (#1677)
  • Handle factors with NAs in pandas.rpy (#1615)
  • Fix statsmodels import in pandas.stats.var (#1734)
  • Fix DataFrame repr/info summary with non-unique columns (#1700)
  • Fix Series.iget_value for non-unique indexes (#1694)
  • Don't lose tzinfo when passing DatetimeIndex as DataFrame column (#1682)
  • Fix tz conversion with time zones that haven't had any DST transitions since first date in the array (#1673)
  • Fix field access with UTC->local conversion on unsorted arrays (#1756)
  • Fix isnull handling of array-like (list) inputs (#1755)
  • Fix regression in handling of Series in Series constructor (#1671)
  • Fix comparison of Int64Index with DatetimeIndex (#1681)
  • Fix min_periods handling in new rolling_max/min at array start (#1695)
  • Fix errors with how='median' and generic NumPy resampling in some cases caused by SeriesBinGrouper (#1648, #1688)
  • When grouping by level, exclude unobserved levels (#1697)
  • Don't lose tzinfo in DatetimeIndex when shifting by different offset (#1683)
  • Hack to support storing data with a zero-length axis in HDFStore (#1707)
  • Fix DatetimeIndex tz-aware range generation issue (#1674)
  • Fix method='time' interpolation with intraday data (#1698)
  • Don't plot all-NA DataFrame columns as zeros (#1696)
  • Fix bug in scatter_plot with by option (#1716)
  • Fix performance problem in infer_freq with lots of non-unique stamps (#1686)
  • Fix handling of PeriodIndex as argument to create MultiIndex (#1705)
  • Fix re: unicode MultiIndex level names in Series/DataFrame repr (#1736)
  • Handle PeriodIndex in to_datetime instance method (#1703)
  • Support StaticTzInfo in DatetimeIndex infrastructure (#1692)
  • Allow MultiIndex setops with length-0 other type indexes (#1727)
  • Fix handling of DatetimeIndex in DataFrame.to_records (#1720)
  • Fix handling of general objects in isnull on which bool(...) fails (#1749)
  • Fix .ix indexing with MultiIndex ambiguity (#1678)
  • Fix .ix setting logic error with non-unique MultiIndex (#1750)
  • Basic indexing now works on MultiIndex with > 1000000 elements, regression from earlier version of pandas (#1757)
  • Handle non-float64 dtypes in fast DataFrame.corr/cov code paths (#1761)
  • Fix DatetimeIndex.isin to function properly (#1763)
  • Fix conversion of array of tz-aware datetime.datetime to DatetimeIndex with right time zone (#1777)
  • Fix DST issues with generating ancxhored date ranges (#1778)
  • Fix issue calling sort on result of Series.unique (#1807)
  • Fix numerical issue leading to square root of negative number in rolling_std (#1840)
  • Let Series.str.split accept no arguments (like str.split) (#1859)
  • Allow user to have dateutil 2.1 installed on a Python 2 system (#1851)
  • Catch ImportError less aggressively in pandas/ (#1845)
  • Fix pip source installation bug when installing from GitHub (#1805)
  • Fix error when window size > array size in rolling_apply (#1850)
  • Fix pip source installation issues via SSH from GitHub
  • Fix OLS.summary when column is a tuple (#1837)
  • Fix bug in __doc__ patching when -OO passed to interpreter (#1792 #1741 #1774)
  • Fix unicode console encoding issue in IPython notebook (#1782, #1768)
  • Fix unicode formatting issue with (#1782)
  • Fix bug in DataFrame.duplicated with datetime64 columns (#1833)
  • Fix bug in Panel internals resulting in error when doing fillna after truncate not changing size of panel (#1823)
  • Prevent segfault due to MultiIndex not being supported in HDFStore table format (#1848)
  • Fix UnboundLocalError in Panel.__setitem__ and add better error (#1826)
  • Fix to_csv issues with list of string entries. Isnull works on list of strings now too (#1791)
  • Fix Timestamp comparisons with datetime values outside the nanosecond range (1677-2262)
  • Revert to prior behavior of normalize_date with objects (return datetime)
  • Fix broken interaction between np.nansum and Series.any/all
  • Fix bug with multiple column date parsers (#1866)
  • DatetimeIndex.union(Int64Index) was broken
  • Make plot x vs y interface consistent with integer indexing (#1842)
  • set_index inplace modified data even if unique check fails (#1831)
  • Only use Q-OCT/NOV/DEC in quarterly frequency inference (#1789)
  • Upcast to dtype=object when unstacking boolean DataFrame (#1820)
  • Fix float64/float32 merging bug (#1849)
  • Fixes to Period.start_time for non-daily frequencies (#1857)
  • Fix failure when converter used on index_col in read_csv (#1835)
  • Implement PeriodIndex.append so that pandas.concat works correctly (#1815)
  • Avoid Cython out-of-bounds access causing segfault sometimes in pad_2d, backfill_2d
  • Fix resampling error with intraday times and anchored target time (like AS-DEC) (#1772)
  • Fix .ix indexing bugs with mixed-integer indexes (#1799)
  • Respect passed color keyword argument in Series.plot (#1890)
  • Fix rolling_min/max when the window is larger than the size of the input array. Check other malformed inputs (#1899, #1897)
  • Rolling variance / standard deviation with only a single observation in window (#1884)
  • Fix unicode sheet name failure in to_excel (#1828)
  • Override DatetimeIndex.min/max to return Timestamp objects (#1895)
  • Fix column name formatting issue in length-truncated column (#1906)
  • Fix broken handling of copying Index metadata to new instances created by view(...) calls inside the NumPy infrastructure
  • Support again in DateOffset.rollback/rollforward
  • Raise Exception if set passed to Series constructor (#1913)
  • Add TypeError when appending HDFStore table w/ wrong index type (#1881)
  • Don't raise exception on empty inputs in EW functions (e.g. ewma) (#1900)
  • Make asof work correctly with PeriodIndex (#1883)
  • Fix extlinks in doc build
  • Fill boolean DataFrame with NaN when calling shift (#1814)
  • Fix setuptools bug causing pip not to Cythonize .pyx files sometimes
  • Fix negative integer indexing regression in .ix from 0.7.x (#1888)
  • Fix error while retrieving timezone and utc offset from subclasses of datetime.tzinfo without .zone and ._utcoffset attributes (#1922)
  • Fix DataFrame formatting of small, non-zero FP numbers (#1911)
  • Various fixes by upcasting of date -> datetime (#1395)
  • Raise better exception when passing multiple functions with the same name, such as lambdas, to GroupBy.aggregate
  • Fix DataFrame.apply with axis=1 on a non-unique index (#1878)
  • Proper handling of Index subclasses in pandas.unique (#1759)
  • Set index names in DataFrame.from_records (#1744)
  • Fix time series indexing error with duplicates, under and over hash table size cutoff (#1821)
  • Handle list keys in addition to tuples in DataFrame.xs when partial-indexing a hierarchically-indexed DataFrame (#1796)
  • Support multiple column selection in DataFrame.__getitem__ with duplicate columns (#1943)
  • Fix time zone localization bug causing improper fields (e.g. hours) in time zones that have not had a UTC transition in a long time (#1946)
  • Fix errors when parsing and working with with fixed offset timezones (#1922, #1928)
  • Fix text parser bug when handling UTC datetime objects generated by dateutil (#1693)
  • Fix plotting bug when 'B' is the inferred frequency but index actually contains weekends (#1668, #1669)
  • Fix plot styling bugs (#1666, #1665, #1658)
  • Fix plotting bug with index/columns with unicode (#1685)
  • Fix DataFrame constructor bug when passed Series with datetime64 dtype in a dict (#1680)
  • Fixed regression in generating DatetimeIndex using timezone aware datetime.datetime (#1676)
  • Fix DataFrame bug when printing concatenated DataFrames with duplicated columns (#1675)
  • Fixed bug when plotting time series with multiple intraday frequencies (#1732)
  • Fix bug in DataFrame.duplicated to enable iterables other than list-types as input argument (#1773)
  • Fix resample bug when passed list of lambdas as how argument (#1808)
  • Repr fix for MultiIndex level with all NAs (#1971)
  • Fix PeriodIndex slicing bug when slice start/end are out-of-bounds (#1977)
  • Fix read_table bug when parsing unicode (#1975)
  • Fix BlockManager.iget bug when dealing with non-unique MultiIndex as columns (#1970)
  • Fix reset_index bug if both drop and level are specified (#1957)
  • Work around unsafe NumPy object->int casting with Cython function (#1987)
  • Fix datetime64 formatting bug in DataFrame.to_csv (#1993)
  • Default start date in to 1/1/2000 as the docs say (#2011)

pandas 0.8.1

Release date: July 22, 2012

New features

  • Add vectorized, NA-friendly string methods to Series (#1621, #620)
  • Can pass dict of per-column line styles to DataFrame.plot (#1559)
  • Selective plotting to secondary y-axis on same subplot (PR #1640)
  • Add new bootstrap_plot plot function
  • Add new parallel_coordinates plot function (#1488)
  • Add radviz plot function (#1566)
  • Add multi_sparse option to set_printoptions to modify display of hierarchical indexes (#1538)
  • Add dropna method to Panel (#171)

Improvements to existing features

  • Use moving min/max algorithms from Bottleneck in rolling_min/rolling_max for > 100x speedup. (#1504, #50)
  • Add Cython group median method for >15x speedup (#1358)
  • Drastically improve to_datetime performance on ISO8601 datetime strings (with no time zones) (#1571)
  • Improve single-key groupby performance on large data sets, accelerate use of groupby with a Categorical variable
  • Add ability to append hierarchical index levels with set_index and to drop single levels with reset_index (#1569, #1577)
  • Always apply passed functions in resample, even if upsampling (#1596)
  • Avoid unnecessary copies in DataFrame constructor with explicit dtype (#1572)
  • Cleaner DatetimeIndex string representation with 1 or 2 elements (#1611)
  • Improve performance of array-of-Period to PeriodIndex, convert such arrays to PeriodIndex inside Index (#1215)
  • More informative string representation for weekly Period objects (#1503)
  • Accelerate 3-axis multi data selection from homogeneous Panel (#979)
  • Add adjust option to ewma to disable adjustment factor (#1584)
  • Add new matplotlib converters for high frequency time series plotting (#1599)
  • Handling of tz-aware datetime.datetime objects in to_datetime; raise Exception unless utc=True given (#1581)

Bug fixes

  • Fix NA handling in DataFrame.to_panel (#1582)
  • Handle TypeError issues inside PyObject_RichCompareBool calls in khash (#1318)
  • Fix resampling bug to lower case daily frequency (#1588)
  • Fix kendall/spearman DataFrame.corr bug with no overlap (#1595)
  • Fix bug in DataFrame.set_index (#1592)
  • Don't ignore axes in boxplot if by specified (#1565)
  • Fix Panel .ix indexing with integers bug (#1603)
  • Fix Partial indexing bugs (years, months, ...) with PeriodIndex (#1601)
  • Fix MultiIndex console formatting issue (#1606)
  • Unordered index with duplicates doesn't yield scalar location for single entry (#1586)
  • Fix resampling of tz-aware time series with "anchored" freq (#1591)
  • Fix DataFrame.rank error on integer data (#1589)
  • Selection of multiple SparseDataFrame columns by list in __getitem__ (#1585)
  • Override Index.tolist for compatibility with MultiIndex (#1576)
  • Fix hierarchical summing bug with MultiIndex of length 1 (#1568)
  • Work around numpy.concatenate use/bug in Series.set_value (#1561)
  • Ensure Series/DataFrame are sorted before resampling (#1580)
  • Fix unhandled IndexError when indexing very large time series (#1562)
  • Fix DatetimeIndex intersection logic error with irregular indexes (#1551)
  • Fix unit test errors on Python 3 (#1550)
  • Fix .ix indexing bugs in duplicate DataFrame index (#1201)
  • Better handle errors with non-existing objects in HDFStore (#1254)
  • Don't copy int64 array data in DatetimeIndex when copy=False (#1624)
  • Fix resampling of conforming periods quarterly to annual (#1622)
  • Don't lose index name on resampling (#1631)
  • Support python-dateutil version 2.1 (#1637)
  • Fix broken scatter_matrix axis labeling, esp. with time series (#1625)
  • Fix cases where extra keywords weren't being passed on to matplotlib from Series.plot (#1636)
  • Fix BusinessMonthBegin logic for dates before 1st bday of month (#1645)
  • Ensure string alias converted (valid in DatetimeIndex.get_loc) in DataFrame.xs / __getitem__ (#1644)
  • Fix use of string alias timestamps with tz-aware time series (#1647)
  • Fix Series.max/min and Series.describe on len-0 series (#1650)
  • Handle None values in dict passed to concat (#1649)
  • Fix Series.interpolate with method='values' and DatetimeIndex (#1646)
  • Fix IndexError in left merges on a DataFrame with 0-length (#1628)
  • Fix DataFrame column width display with UTF-8 encoded characters (#1620)
  • Handle case in where Yahoo! returns duplicate dates for most recent business day
  • Avoid downsampling when plotting mixed frequencies on the same subplot (#1619)
  • Fix read_csv bug when reading a single line (#1553)
  • Fix bug in C code causing monthly periods prior to December 1969 to be off (#1570)

pandas 0.8.0

Release date: 6/29/2012

New features

  • New unified DatetimeIndex class for nanosecond-level timestamp data
  • New Timestamp datetime.datetime subclass with easy time zone conversions, and support for nanoseconds
  • New PeriodIndex class for timespans, calendar logic, and Period scalar object
  • High performance resampling of timestamp and period data. New resample method of all pandas data structures
  • New frequency names plus shortcut string aliases like '15h', '1h30min'
  • Time series string indexing shorthand (#222)
  • Add week, dayofyear array and other timestamp array-valued field accessor functions to DatetimeIndex
  • Add optimized aggregation function and 'prod' fast time series conversion method (#1018)
  • Implement robust frequency inference function and inferred_freq attribute on DatetimeIndex (#391)
  • New tz_convert and tz_localize methods in Series / DataFrame
  • Convert DatetimeIndexes to UTC if time zones are different in join/setops (#864)
  • Add limit argument for forward/backward filling to reindex, fillna, etc. (#825 and others)
  • Add support for indexes (dates or otherwise) with duplicates and common sense indexing/selection functionality
  • Series/DataFrame.update methods, in-place variant of combine_first (#961)
  • Add match function to API (#502)
  • Add Cython-optimized first, last, min, max, prod functions to GroupBy (#994, #1043)
  • Dates can be split across multiple columns (#1227, #1186)
  • Add experimental support for converting pandas DataFrame to R data.frame via rpy2 (#350, #1212)
  • Can pass list of (name, function) to GroupBy.aggregate to get aggregates in a particular order (#610)
  • Can pass dicts with lists of functions or dicts to GroupBy aggregate to do much more flexible multiple function aggregation (#642, #610)
  • New ordered_merge functions for merging DataFrames with ordered data. Also supports group-wise merging for panel data (#813)
  • Add keys() method to DataFrame
  • Add flexible replace method for replacing potentially values to Series and DataFrame (#929, #1241)
  • Add 'kde' plot kind for Series/DataFrame.plot (#1059)
  • More flexible multiple function aggregation with GroupBy
  • Add pct_change function to Series/DataFrame
  • Add option to interpolate by Index values in Series.interpolate (#1206)
  • Add max_colwidth option for DataFrame, defaulting to 50
  • Conversion of DataFrame through rpy2 to R data.frame (#1282, )
  • Add keys() method on DataFrame (#1240)
  • Add new match function to API (similar to R) (#502)
  • Add dayfirst option to parsers (#854)
  • Add method argument to align method for forward/backward fillin (#216)
  • Add Panel.transpose method for rearranging axes (#695)
  • Add new cut function (patterned after R) for discretizing data into equal range-length bins or arbitrary breaks of your choosing (#415)
  • Add new qcut for cutting with quantiles (#1378)
  • Add value_counts top level array method (#1392)
  • Added Andrews curves plot tupe (#1325)
  • Add lag plot (#1440)
  • Add autocorrelation_plot (#1425)
  • Add support for tox and Travis CI (#1382)
  • Add support for Categorical use in GroupBy (#292)
  • Add any and all methods to DataFrame (#1416)
  • Add secondary_y option to Series.plot
  • Add experimental lreshape function for reshaping wide to long

Improvements to existing features

  • Switch to klib/khash-based hash tables in Index classes for better performance in many cases and lower memory footprint
  • Shipping some functions from scipy.stats to reduce dependency, e.g. Series.describe and DataFrame.describe (GH #1092)
  • Can create MultiIndex by passing list of lists or list of arrays to Series, DataFrame constructor, etc. (#831)
  • Can pass arrays in addition to column names to DataFrame.set_index (#402)
  • Improve the speed of "square" reindexing of homogeneous DataFrame objects by significant margin (#836)
  • Handle more dtypes when passed MaskedArrays in DataFrame constructor (#406)
  • Improved performance of join operations on integer keys (#682)
  • Can pass multiple columns to GroupBy object, e.g. grouped[[col1, col2]] to only aggregate a subset of the value columns (#383)
  • Add histogram / kde plot options for scatter_matrix diagonals (#1237)
  • Add inplace option to Series/DataFrame.rename and sort_index, DataFrame.drop_duplicates (#805, #207)
  • More helpful error message when nothing passed to Series.reindex (#1267)
  • Can mix array and scalars as dict-value inputs to DataFrame ctor (#1329)
  • Use DataFrame columns' name for legend title in plots
  • Preserve frequency in DatetimeIndex when possible in boolean indexing operations
  • Promote values in data alignment operations (#867)
  • Add order method to Index classes (#1028)
  • Avoid hash table creation in large monotonic hash table indexes (#1160)
  • Store time zones in HDFStore (#1232)
  • Enable storage of sparse data structures in HDFStore (#85)
  • Enable Series.asof to work with arrays of timestamp inputs
  • Cython implementation of DataFrame.corr speeds up by > 100x (#1349, #1354)
  • Exclude "nuisance" columns automatically in GroupBy.transform (#1364)
  • Support functions-as-strings in GroupBy.transform (#1362)
  • Use index name as xlabel/ylabel in plots (#1415)
  • Add convert_dtype option to Series.apply to be able to leave data as dtype=object (#1414)
  • Can specify all index level names in concat (#1419)
  • Add dialect keyword to parsers for quoting conventions (#1363)
  • Enable DataFrame[bool_DataFrame] += value (#1366)
  • Add retries argument to get_data_yahoo to try to prevent Yahoo! API 404s (#826)
  • Improve performance of reshaping by using O(N) categorical sorting
  • Series names will be used for index of DataFrame if no index passed (#1494)
  • Header argument in DataFrame.to_csv can accept a list of column names to use instead of the object's columns (#921)
  • Add raise_conflict argument to DataFrame.update (#1526)
  • Support file-like objects in ExcelFile (#1529)

API Changes

  • Rename pandas._tseries to pandas.lib
  • Rename Factor to Categorical and add improvements. Numerous Categorical bug fixes
  • Frequency name overhaul, WEEKDAY/EOM and rules with @ deprecated. get_legacy_offset_name backwards compatibility function added
  • Raise ValueError in DataFrame.__nonzero__, so "if df" no longer works (#1073)
  • Change BDay (business day) to not normalize dates by default (#506)
  • Remove deprecated DataMatrix name
  • Default merge suffixes for overlap now have underscores instead of periods to facilitate tab completion, etc. (#1239)
  • Deprecation of offset, time_rule timeRule parameters throughout codebase
  • Series.append and DataFrame.append no longer check for duplicate indexes by default, add verify_integrity parameter (#1394)
  • Refactor Factor class, old constructor moved to Factor.from_array
  • Modified internals of MultiIndex to use less memory (no longer represented as array of tuples) internally, speed up construction time and many methods which construct intermediate hierarchical indexes (#1467)

Bug fixes

  • Fix OverflowError from storing pre-1970 dates in HDFStore by switching to datetime64 (GH #179)
  • Fix logical error with February leap year end in YearEnd offset
  • Series([False, nan]) was getting casted to float64 (GH #1074)
  • Fix binary operations between boolean Series and object Series with booleans and NAs (GH #1074, #1079)
  • Couldn't assign whole array to column in mixed-type DataFrame via .ix (#1142)
  • Fix label slicing issues with float index values (#1167)
  • Fix segfault caused by empty groups passed to groupby (#1048)
  • Fix occasionally misbehaved reindexing in the presence of NaN labels (#522)
  • Fix imprecise logic causing weird Series results from .apply (#1183)
  • Unstack multiple levels in one shot, avoiding empty columns in some cases. Fix pivot table bug (#1181)
  • Fix formatting of MultiIndex on Series/DataFrame when index name coincides with label (#1217)
  • Handle Excel 2003 #N/A as NaN from xlrd (#1213, #1225)
  • Fix timestamp locale-related deserialization issues with HDFStore by moving to datetime64 representation (#1081, #809)
  • Fix DataFrame.duplicated/drop_duplicates NA value handling (#557)
  • Actually raise exceptions in fast reducer (#1243)
  • Fix various timezone-handling bugs from 0.7.3 (#969)
  • GroupBy on level=0 discarded index name (#1313)
  • Better error message with unmergeable DataFrames (#1307)
  • Series.__repr__ alignment fix with unicode index values (#1279)
  • Better error message if nothing passed to reindex (#1267)
  • More robust NA handling in DataFrame.drop_duplicates (#557)
  • Resolve locale-based and pre-epoch HDF5 timestamp deserialization issues (#973, #1081, #179)
  • Implement Series.repeat (#1229)
  • Fix indexing with namedtuple and other tuple subclasses (#1026)
  • Fix float64 slicing bug (#1167)
  • Parsing integers with commas (#796)
  • Fix groupby improper data type when group consists of one value (#1065)
  • Fix negative variance possibility in nanvar resulting from floating point error (#1090)
  • Consistently set name on groupby pieces (#184)
  • Treat dict return values as Series in GroupBy.apply (#823)
  • Respect column selection for DataFrame in in GroupBy.transform (#1365)
  • Fix MultiIndex partial indexing bug (#1352)
  • Enable assignment of rows in mixed-type DataFrame via .ix (#1432)
  • Reset index mapping when grouping Series in Cython (#1423)
  • Fix outer/inner DataFrame.join with non-unique indexes (#1421)
  • Fix MultiIndex groupby bugs with empty lower levels (#1401)
  • Calling fillna with a Series will have same behavior as with dict (#1486)
  • SparseSeries reduction bug (#1375)
  • Fix unicode serialization issue in HDFStore (#1361)
  • Pass keywords to pyplot.boxplot in DataFrame.boxplot (#1493)
  • Bug fixes in MonthBegin (#1483)
  • Preserve MultiIndex names in drop (#1513)
  • Fix Panel DataFrame slice-assignment bug (#1533)
  • Don't use locals() in read_* functions (#1547)

pandas 0.7.3

Release date: April 12, 2012

New features / modules

  • Support for non-unique indexes: indexing and selection, many-to-one and many-to-many joins (#1306)
  • Added fixed-width file reader, read_fwf (PR #952)
  • Add group_keys argument to groupby to not add group names to MultiIndex in result of apply (GH #938)
  • DataFrame can now accept non-integer label slicing (GH #946). Previously only DataFrame.ix was able to do so.
  • DataFrame.apply now retains name attributes on Series objects (GH #983)
  • Numeric DataFrame comparisons with non-numeric values now raises proper TypeError (GH #943). Previously raise "PandasError: DataFrame constructor not properly called!"
  • Add kurt methods to Series and DataFrame (PR #964)
  • Can pass dict of column -> list/set NA values for text parsers (GH #754)
  • Allows users specified NA values in text parsers (GH #754)
  • Parsers checks for openpyxl dependency and raises ImportError if not found (PR #1007)
  • New factory function to create HDFStore objects that can be used in a with statement so users do not have to explicitly call HDFStore.close (PR #1005)
  • pivot_table is now more flexible with same parameters as groupby (GH #941)
  • Added stacked bar plots (GH #987)
  • scatter_matrix method in pandas/tools/ (PR #935)
  • DataFrame.boxplot returns plot results for ex-post styling (GH #985)
  • Short version number accessible as pandas.version.short_version (GH #930)
  • Additional documentation in panel.to_frame (GH #942)
  • More informative Series.apply docstring regarding element-wise apply (GH #977)
  • Notes on rpy2 installation (GH #1006)
  • Add rotation and font size options to hist method (#1012)
  • Use exogenous / X variable index in result of OLS.y_predict. Add OLS.predict method (PR #1027, #1008)

API Changes

  • Calling apply on grouped Series, e.g. describe(), will no longer yield DataFrame by default. Will have to call unstack() to get prior behavior
  • NA handling in non-numeric comparisons has been tightened up (#933, #953)
  • No longer assign dummy names key_0, key_1, etc. to groupby index (#1291)

Bug fixes

  • Fix logic error when selecting part of a row in a DataFrame with a MultiIndex index (GH #1013)
  • Series comparison with Series of differing length causes crash (GH #1016).
  • Fix bug in indexing when selecting section of hierarchically-indexed row (GH #1013)
  • DataFrame.plot(logy=True) has no effect (GH #1011).
  • Broken arithmetic operations between SparsePanel-Panel (GH #1015)
  • Unicode repr issues in MultiIndex with non-ascii characters (GH #1010)
  • DataFrame.lookup() returns inconsistent results if exact match not present (GH #1001)
  • DataFrame arithmetic operations not treating None as NA (GH #992)
  • DataFrameGroupBy.apply returns incorrect result (GH #991)
  • Series.reshape returns incorrect result for multiple dimensions (GH #989)
  • Series.std and Series.var ignores ddof parameter (GH #934)
  • DataFrame.append loses index names (GH #980)
  • DataFrame.plot(kind='bar') ignores color argument (GH #958)
  • Inconsistent Index comparison results (GH #948)
  • Improper int dtype DataFrame construction from data with NaN (GH #846)
  • Removes default 'result' name in grouby results (GH #995)
  • DataFrame.from_records no longer mutate input columns (PR #975)
  • Use Index name when grouping by it (#1313)

pandas 0.7.2

Release date: March 16, 2012

New features / modules

  • Add additional tie-breaking methods in DataFrame.rank (#874)
  • Add ascending parameter to rank in Series, DataFrame (#875)
  • Add coerce_float option to DataFrame.from_records (#893)
  • Add sort_columns parameter to allow unsorted plots (#918)
  • IPython tab completion on GroupBy objects

API Changes

  • Series.sum returns 0 instead of NA when called on an empty series. Analogously for a DataFrame whose rows or columns are length 0 (#844)

Improvements to existing features

  • Don't use groups dict in Grouper.size (#860)
  • Use khash for Series.value_counts, add raw function to (#861)
  • Enable column access via attributes on GroupBy (#882)
  • Enable setting existing columns (only) via attributes on DataFrame, Panel (#883)
  • Intercept __builtin__.sum in groupby (#885)
  • Can pass dict to DataFrame.fillna to use different values per column (#661)
  • Can select multiple hierarchical groups by passing list of values in .ix (#134)
  • Add level keyword to drop for dropping values from a level (GH #159)
  • Add coerce_float option on DataFrame.from_records (# 893)
  • Raise exception if passed date_parser fails in read_csv
  • Add axis option to DataFrame.fillna (#174)
  • Fixes to Panel to make it easier to subclass (PR #888)

Bug fixes

  • Fix overflow-related bugs in groupby (#850, #851)
  • Fix unhelpful error message in parsers (#856)
  • Better err msg for failed boolean slicing of dataframe (#859)
  • Series.count cannot accept a string (level name) in the level argument (#869)
  • Group index platform int check (#870)
  • concat on axis=1 and ignore_index=True raises TypeError (#871)
  • Further unicode handling issues resolved (#795)
  • Fix failure in multiindex-based access in Panel (#880)
  • Fix DataFrame boolean slice assignment failure (#881)
  • Fix combineAdd NotImplementedError for SparseDataFrame (#887)
  • Fix DataFrame.to_html encoding and columns (#890, #891, #909)
  • Fix na-filling handling in mixed-type DataFrame (#910)
  • Fix to DataFrame.set_value with non-existant row/col (#911)
  • Fix malformed block in groupby when excluding nuisance columns (#916)
  • Fix inconsistant NA handling in dtype=object arrays (#925)
  • Fix missing center-of-mass computation in ewmcov (#862)
  • Don't raise exception when opening read-only HDF5 file (#847)
  • Fix possible out-of-bounds memory access in 0-length Series (#917)

pandas 0.7.1

Release date: February 29, 2012

New features / modules

  • Add to_clipboard function to pandas namespace for writing objects to the system clipboard (#774)
  • Add itertuples method to DataFrame for iterating through the rows of a dataframe as tuples (#818)
  • Add ability to pass fill_value and method to DataFrame and Series align method (#806, #807)
  • Add fill_value option to reindex, align methods (#784)
  • Enable concat to produce DataFrame from Series (#787)
  • Add between method to Series (#802)
  • Add HTML representation hook to DataFrame for the IPython HTML notebook (#773)
  • Support for reading Excel 2007 XML documents using openpyxl

Improvements to existing features

  • Improve performance and memory usage of fillna on DataFrame
  • Can concatenate a list of Series along axis=1 to obtain a DataFrame (#787)

Bug fixes

  • Fix memory leak when inserting large number of columns into a single DataFrame (#790)
  • Appending length-0 DataFrame with new columns would not result in those new columns being part of the resulting concatenated DataFrame (#782)
  • Fixed groupby corner case when passing dictionary grouper and as_index is False (#819)
  • Fixed bug whereby bool array sometimes had object dtype (#820)
  • Fix exception thrown on np.diff (#816)
  • Fix to_records where columns are non-strings (#822)
  • Fix Index.intersection where indices have incomparable types (#811)
  • Fix ExcelFile throwing an exception for two-line file (#837)
  • Add clearer error message in csv parser (#835)
  • Fix loss of fractional seconds in HDFStore (#513)
  • Fix DataFrame join where columns have datetimes (#787)
  • Work around numpy performance issue in take (#817)
  • Improve comparison operations for NA-friendliness (#801)
  • Fix indexing operation for floating point values (#780, #798)
  • Fix groupby case resulting in malformed dataframe (#814)
  • Fix behavior of reindex of Series dropping name (#812)
  • Improve on redudant groupby computation (#775)
  • Catch possible NA assignment to int/bool series with exception (#839)

pandas 0.7.0

Release date: 2/9/2012

New features / modules

  • New merge function for efficiently performing full gamut of database / relational-algebra operations. Refactored existing join methods to use the new infrastructure, resulting in substantial performance gains (GH #220, #249, #267)
  • New concat function for concatenating DataFrame or Panel objects along an axis. Can form union or intersection of the other axes. Improves performance of DataFrame.append (#468, #479, #273)
  • Handle differently-indexed output values in DataFrame.apply (GH #498)
  • Can pass list of dicts (e.g., a list of shallow JSON objects) to DataFrame constructor (GH #526)
  • Add reorder_levels method to Series and DataFrame (PR #534)
  • Add dict-like get function to DataFrame and Panel (PR #521)
  • DataFrame.iterrows method for efficiently iterating through the rows of a DataFrame
  • Added DataFrame.to_panel with code adapted from LongPanel.to_long
  • reindex_axis method added to DataFrame
  • Add level option to binary arithmetic functions on DataFrame and Series
  • Add level option to the reindex and align methods on Series and DataFrame for broadcasting values across a level (GH #542, PR #552, others)
  • Add attribute-based item access to Panel and add IPython completion (PR #554)
  • Add logy option to Series.plot for log-scaling on the Y axis
  • Add index, header, and justify options to DataFrame.to_string. Add option to (GH #570, GH #571)
  • Can pass multiple DataFrames to DataFrame.join to join on index (GH #115)
  • Can pass multiple Panels to Panel.join (GH #115)
  • Can pass multiple DataFrames to DataFrame.append to concatenate (stack) and multiple Series to Series.append too
  • Added justify argument to DataFrame.to_string to allow different alignment of column headers
  • Add sort option to GroupBy to allow disabling sorting of the group keys for potential speedups (GH #595)
  • Can pass MaskedArray to Series constructor (PR #563)
  • Add Panel item access via attributes and IPython completion (GH #554)
  • Implement DataFrame.lookup, fancy-indexing analogue for retrieving values given a sequence of row and column labels (GH #338)
  • Add verbose option to read_csv and read_table to show number of NA values inserted in non-numeric columns (GH #614)
  • Can pass a list of dicts or Series to DataFrame.append to concatenate multiple rows (GH #464)
  • Add level argument to DataFrame.xs for selecting data from other MultiIndex levels. Can take one or more levels with potentially a tuple of keys for flexible retrieval of data (GH #371, GH #629)
  • New crosstab function for easily computing frequency tables (GH #170)
  • Can pass a list of functions to aggregate with groupby on a DataFrame, yielding an aggregated result with hierarchical columns (GH #166)
  • Add integer-indexing functions iget in Series and irow / iget in DataFrame (GH #628)
  • Add new Series.unique function, significantly faster than numpy.unique (GH #658)
  • Add new cummin and cummax instance methods to Series and DataFrame (GH #647)
  • Add new value_range function to return min/max of a dataframe (GH #288)
  • Add drop parameter to reset_index method of DataFrame and added method to Series as well (GH #699)
  • Add isin method to Index objects, works just like Series.isin (GH #657)
  • Implement array interface on Panel so that ufuncs work (re: #740)
  • Add sort option to DataFrame.join (GH #731)
  • Improved handling of NAs (propagation) in binary operations with dtype=object arrays (GH #737)
  • Add abs method to Pandas objects
  • Added algorithms module to start collecting central algos

API Changes

  • Label-indexing with integer indexes now raises KeyError if a label is not found instead of falling back on location-based indexing (GH #700)
  • Label-based slicing via ix or [] on Series will now only work if exact matches for the labels are found or if the index is monotonic (for range selections)
  • Label-based slicing and sequences of labels can be passed to [] on a Series for both getting and setting (GH #86)
  • [] operator (__getitem__ and __setitem__) will raise KeyError with integer indexes when an index is not contained in the index. The prior behavior would fall back on position-based indexing if a key was not found in the index which would lead to subtle bugs. This is now consistent with the behavior of .ix on DataFrame and friends (GH #328)
  • Rename DataFrame.delevel to DataFrame.reset_index and add deprecation warning
  • Series.sort (an in-place operation) called on a Series which is a view on a larger array (e.g. a column in a DataFrame) will generate an Exception to prevent accidentally modifying the data source (GH #316)
  • Refactor to remove deprecated LongPanel class (PR #552)
  • Deprecated Panel.to_long, renamed to to_frame
  • Deprecated colSpace argument in DataFrame.to_string, renamed to col_space
  • Rename precision to accuracy in engineering float formatter (GH #395)
  • The default delimiter for read_csv is comma rather than letting csv.Sniffer infer it
  • Rename col_or_columns argument in DataFrame.drop_duplicates (GH #734)

Improvements to existing features

  • Better error message in DataFrame constructor when passed column labels don't match data (GH #497)
  • Substantially improve performance of multi-GroupBy aggregation when a Python function is passed, reuse ndarray object in Cython (GH #496)
  • Can store objects indexed by tuples and floats in HDFStore (GH #492)
  • Don't print length by default in Series.to_string, add length option (GH #489)
  • Improve Cython code for multi-groupby to aggregate without having to sort the data (GH #93)
  • Improve MultiIndex reindexing speed by storing tuples in the MultiIndex, test for backwards unpickling compatibility
  • Improve column reindexing performance by using specialized Cython take function
  • Further performance tweaking of Series.__getitem__ for standard use cases
  • Avoid Index dict creation in some cases (i.e. when getting slices, etc.), regression from prior versions
  • Friendlier error message in if NumPy not installed
  • Use common set of NA-handling operations (sum, mean, etc.) in Panel class also (GH #536)
  • Default name assignment when calling reset_index on DataFrame with a regular (non-hierarchical) index (GH #476)
  • Use Cythonized groupers when possible in Series/DataFrame stat ops with level parameter passed (GH #545)
  • Ported skiplist data structure to C to speed up rolling_median by about 5-10x in most typical use cases (GH #374)
  • Some performance enhancements in constructing a Panel from a dict of DataFrame objects
  • Made Index._get_duplicates a public method by removing the underscore
  • Prettier printing of floats, and column spacing fix (GH #395, GH #571)
  • Add bold_rows option to DataFrame.to_html (GH #586)
  • Improve the performance of DataFrame.sort_index by up to 5x or more when sorting by multiple columns
  • Substantially improve performance of DataFrame and Series constructors when passed a nested dict or dict, respectively (GH #540, GH #621)
  • Modified so that pip / setuptools will install dependencies (GH #507, various pull requests)
  • Unstack called on DataFrame with non-MultiIndex will return Series (GH #477)
  • Improve DataFrame.to_string and console formatting to be more consistent in the number of displayed digits (GH #395)
  • Use bottleneck if available for performing NaN-friendly statistical operations that it implemented (GH #91)
  • Monkey-patch context to traceback in DataFrame.apply to indicate which row/column the function application failed on (GH #614)
  • Improved ability of read_table and read_clipboard to parse console-formatted DataFrames (can read the row of index names, etc.)
  • Can pass list of group labels (without having to convert to an ndarray yourself) to groupby in some cases (GH #659)
  • Use kind argument to Series.order for selecting different sort kinds (GH #668)
  • Add option to Series.to_csv to omit the index (PR #684)
  • Add delimiter as an alternative to sep in read_csv and other parsing functions
  • Substantially improved performance of groupby on DataFrames with many columns by aggregating blocks of columns all at once (GH #745)
  • Can pass a file handle or StringIO to Series/DataFrame.to_csv (GH #765)
  • Can pass sequence of integers to DataFrame.irow(icol) and Series.iget, (GH #654)
  • Prototypes for some vectorized string functions
  • Add float64 hash table to solve the Series.unique problem with NAs (GH #714)
  • Memoize objects when reading from file to reduce memory footprint
  • Can get and set a column of a DataFrame with hierarchical columns containing "empty" ('') lower levels without passing the empty levels (PR #768)

Bug fixes

  • Raise exception in out-of-bounds indexing of Series instead of seg-faulting, regression from earlier releases (GH #495)
  • Fix error when joining DataFrames of different dtypes within the same typeclass (e.g. float32 and float64) (GH #486)
  • Fix bug in Series.min/Series.max on objects like datetime.datetime (GH #487)
  • Preserve index names in Index.union (GH #501)
  • Fix bug in Index joining causing subclass information (like DateRange type) to be lost in some cases (GH #500)
  • Accept empty list as input to DataFrame constructor, regression from 0.6.0 (GH #491)
  • Can output DataFrame and Series with ndarray objects in a dtype=object array (GH #490)
  • Return empty string from Series.to_string when called on empty Series (GH #488)
  • Fix exception passing empty list to DataFrame.from_records
  • Fix Index.format bug (excluding name field) with datetimes with time info
  • Fix scalar value access in Series to always return NumPy scalars, regression from prior versions (GH #510)
  • Handle rows skipped at beginning of file in read_* functions (GH #505)
  • Handle improper dtype casting in set_value methods
  • Unary '-' / __neg__ operator on DataFrame was returning integer values
  • Unbox 0-dim ndarrays from certain operators like all, any in Series
  • Fix handling of missing columns (was combine_first-specific) in DataFrame.combine for general case (GH #529)
  • Fix type inference logic with boolean lists and arrays in DataFrame indexing
  • Use centered sum of squares in R-square computation if entity_effects=True in panel regression
  • Handle all NA case in Series.{corr, cov}, was raising exception (GH #548)
  • Aggregating by multiple levels with level argument to DataFrame, Series stat method, was broken (GH #545)
  • Fix Cython buf when converter passed to read_csv produced a numeric array (buffer dtype mismatch when passed to Cython type inference function) (GH #546)
  • Fix exception when setting scalar value using .ix on a DataFrame with a MultiIndex (GH #551)
  • Fix outer join between two DateRanges with different offsets that returned an invalid DateRange
  • Cleanup DataFrame.from_records failure where index argument is an integer
  • Fix Data.from_records failure when passed a dictionary
  • Fix NA handling in {Series, DataFrame}.rank with non-floating point dtypes
  • Fix bug related to integer type-checking in .ix-based indexing
  • Handle non-string index name passed to DataFrame.from_records
  • DataFrame.insert caused the columns name(s) field to be discarded (GH #527)
  • Fix erroneous in monotonic many-to-one left joins
  • Fix DataFrame.to_string to remove extra column white space (GH #571)
  • Format floats to default to same number of digits (GH #395)
  • Added decorator to copy docstring from one function to another (GH #449)
  • Fix error in monotonic many-to-one left joins
  • Fix __eq__ comparison between DateOffsets with different relativedelta keywords passed
  • Fix exception caused by parser converter returning strings (GH #583)
  • Fix MultiIndex formatting bug with integer names (GH #601)
  • Fix bug in handling of non-numeric aggregates in Series.groupby (GH #612)
  • Fix TypeError with tuple subclasses (e.g. namedtuple) in DataFrame.from_records (GH #611)
  • Catch misreported console size when running IPython within Emacs
  • Fix minor bug in pivot table margins, loss of index names and length-1 'All' tuple in row labels
  • Add support for legacy WidePanel objects to be read from HDFStore
  • Fix out-of-bounds segfault in pad_object and backfill_object methods when either source or target array are empty
  • Could not create a new column in a DataFrame from a list of tuples
  • Fix bugs preventing SparseDataFrame and SparseSeries working with groupby (GH #666)
  • Use sort kind in Series.sort / argsort (GH #668)
  • Fix DataFrame operations on non-scalar, non-pandas objects (GH #672)
  • Don't convert DataFrame column to integer type when passing integer to __setitem__ (GH #669)
  • Fix downstream bug in pivot_table caused by integer level names in MultiIndex (GH #678)
  • Fix SparseSeries.combine_first when passed a dense Series (GH #687)
  • Fix performance regression in HDFStore loading when DataFrame or Panel stored in table format with datetimes
  • Raise Exception in DateRange when offset with n=0 is passed (GH #683)
  • Fix get/set inconsistency with .ix property and integer location but non-integer index (GH #707)
  • Use right dropna function for SparseSeries. Return dense Series for NA fill value (GH #730)
  • Fix Index.format bug causing incorrectly string-formatted Series with datetime indexes (# 726, 758)
  • Fix errors caused by object dtype arrays passed to ols (GH #759)
  • Fix error where column names lost when passing list of labels to DataFrame.__getitem__, (GH #662)
  • Fix error whereby top-level week iterator overwrote week instance
  • Fix circular reference causing memory leak in sparse array / series / frame, (GH #663)
  • Fix integer-slicing from integers-as-floats (GH #670)
  • Fix zero division errors in nanops from object dtype arrays in all NA case (GH #676)
  • Fix csv encoding when using unicode (GH #705, #717, #738)
  • Fix assumption that each object contains every unique block type in concat, (GH #708)
  • Fix sortedness check of multiindex in to_panel (GH #719, 720)
  • Fix that None was not treated as NA in PyObjectHashtable
  • Fix hashing dtype because of endianness confusion (GH #747, #748)
  • Fix SparseSeries.dropna to return dense Series in case of NA fill value (GH #730)
  • Use map_infer instead of np.vectorize. handle NA sentinels if converter yields numeric array, (GH #753)
  • Fixes and improvements to DataFrame.rank (GH #742)
  • Fix catching AttributeError instead of NameError for bottleneck
  • Try to cast non-MultiIndex to better dtype when calling reset_index (GH #726 #440)
  • Fix #1.QNAN0' float bug on 2.6/win64
  • Allow subclasses of dicts in DataFrame constructor, with tests
  • Fix problem whereby set_index destroys column multiindex (GH #764)
  • Hack around bug in generating DateRange from naive DateOffset (GH #770)
  • Fix bug in DateRange.intersection causing incorrect results with some overlapping ranges (GH #771)


  • Craig Austin
  • Chris Billington
  • Marius Cobzarenco
  • Mario Gamboa-Cavazos
  • Hans-Martin Gaudecker
  • Arthur Gerigk
  • Yaroslav Halchenko
  • Jeff Hammerbacher
  • Matt Harrison
  • Andreas Hilboll
  • Luc Kesters
  • Adam Klein
  • Gregg Lind
  • Solomon Negusse
  • Wouter Overmeire
  • Christian Prinoth
  • Jeff Reback
  • Sam Reckoner
  • Craig Reeson
  • Jan Schulz
  • Skipper Seabold
  • Ted Square
  • Graham Taylor
  • Aman Thakral
  • Chris Uga
  • Dieter Vandenbussche
  • Texas P.
  • Pinxing Ye
  • ... and everyone I forgot

pandas 0.6.1

Release date: 12/13/2011

API Changes

  • Rename names argument in DataFrame.from_records to columns. Add deprecation warning
  • Boolean get/set operations on Series with boolean Series will reindex instead of requiring that the indexes be exactly equal (GH #429)

New features / modules

  • Can pass Series to DataFrame.append with ignore_index=True for appending a single row (GH #430)
  • Add Spearman and Kendall correlation options to Series.corr and DataFrame.corr (GH #428)
  • Add new get_value and set_value methods to Series, DataFrame, and Panel to very low-overhead access to scalar elements. df.get_value(row, column) is about 3x faster than df[column][row] by handling fewer cases (GH #437, #438). Add similar methods to sparse data structures for compatibility
  • Add Qt table widget to sandbox (PR #435)
  • DataFrame.align can accept Series arguments, add axis keyword (GH #461)
  • Implement new SparseList and SparseArray data structures. SparseSeries now derives from SparseArray (GH #463)
  • max_columns / max_rows options in set_printoptions (PR #453)
  • Implement Series.rank and DataFrame.rank, fast versions of scipy.stats.rankdata (GH #428)
  • Implement DataFrame.from_items alternate constructor (GH #444)
  • DataFrame.convert_objects method for inferring better dtypes for object columns (GH #302)
  • Add rolling_corr_pairwise function for computing Panel of correlation matrices (GH #189)
  • Add margins option to pivot_table for computing subgroup aggregates (GH #114)
  • Add Series.from_csv function (PR #482)

Improvements to existing features

  • Improve memory usage of DataFrame.describe (do not copy data unnecessarily) (PR #425)
  • Use same formatting function for outputting floating point Series to console as in DataFrame (PR #420)
  • DataFrame.delevel will try to infer better dtype for new columns (GH #440)
  • Exclude non-numeric types in DataFrame.{corr, cov}
  • Override Index.astype to enable dtype casting (GH #412)
  • Use same float formatting function for Series.__repr__ (PR #420)
  • Use available console width to output DataFrame columns (PR #453)
  • Accept ndarrays when setting items in Panel (GH #452)
  • Infer console width when printing __repr__ of DataFrame to console (PR #453)
  • Optimize scalar value lookups in the general case by 25% or more in Series and DataFrame
  • Can pass DataFrame/DataFrame and DataFrame/Series to rolling_corr/rolling_cov (GH #462)
  • Fix performance regression in cross-sectional count in DataFrame, affecting DataFrame.dropna speed
  • Column deletion in DataFrame copies no data (computes views on blocks) (GH #158)
  • MultiIndex.get_level_values can take the level name
  • More helpful error message when DataFrame.plot fails on one of the columns (GH #478)
  • Improve performance of DataFrame.{index, columns} attribute lookup

Bug fixes

  • Fix O(K^2) memory leak caused by inserting many columns without consolidating, had been present since 0.4.0 (GH #467)
  • DataFrame.count should return Series with zero instead of NA with length-0 axis (GH #423)
  • Fix Yahoo! Finance API usage in (GH #419, PR #427)
  • Fix upstream bug causing failure in Series.align with empty Series (GH #434)
  • Function passed to DataFrame.apply can return a list, as long as it's the right length. Regression from 0.4 (GH #432)
  • Don't "accidentally" upcast scalar values when indexing using .ix (GH #431)
  • Fix groupby exception raised with as_index=False and single column selected (GH #421)
  • Implement DateOffset.__ne__ causing downstream bug (GH #456)
  • Fix __doc__-related issue when converting py -> pyo with py2exe
  • Bug fix in left join Cython code with duplicate monotonic labels
  • Fix bug when unstacking multiple levels described in #451
  • Exclude NA values in dtype=object arrays, regression from 0.5.0 (GH #469)
  • Use Cython map_infer function in DataFrame.applymap to properly infer output type, handle tuple return values and other things that were breaking (GH #465)
  • Handle floating point index values in HDFStore (GH #454)
  • Fixed stale column reference bug (cached Series object) caused by type change / item deletion in DataFrame (GH #473)
  • Index.get_loc should always raise Exception when there are duplicates
  • Handle differently-indexed Series input to DataFrame constructor (GH #475)
  • Omit nuisance columns in multi-groupby with Python function
  • Buglet in handling of single grouping in general apply
  • Handle type inference properly when passing list of lists or tuples to DataFrame constructor (GH #484)
  • Preserve Index / MultiIndex names in GroupBy.apply concatenation step (GH #481)


  • Ralph Bean
  • Luca Beltrame
  • Marius Cobzarenco
  • Andreas Hilboll
  • Jev Kuznetsov
  • Adam Lichtenstein
  • Wouter Overmeire
  • Fernando Perez
  • Nathan Pinger
  • Christian Prinoth
  • Alex Reyfman
  • Joon Ro
  • Chang She
  • Ted Square
  • Chris Uga
  • Dieter Vandenbussche

pandas 0.6.0

Release date: 11/25/2011

API Changes

  • Arithmetic methods like sum will attempt to sum dtype=object values by default instead of excluding them (GH #382)

New features / modules

  • Add melt function to pandas.core.reshape
  • Add level parameter to group by level in Series and DataFrame descriptive statistics (PR #313)
  • Add head and tail methods to Series, analogous to to DataFrame (PR #296)
  • Add Series.isin function which checks if each value is contained in a passed sequence (GH #289)
  • Add float_format option to Series.to_string
  • Add skip_footer (GH #291) and converters (GH #343) options to read_csv and read_table
  • Add proper, tested weighted least squares to standard and panel OLS (GH #303)
  • Add drop_duplicates and duplicated functions for removing duplicate DataFrame rows and checking for duplicate rows, respectively (GH #319)
  • Implement logical (boolean) operators &, |, ^ on DataFrame (GH #347)
  • Add Series.mad, mean absolute deviation, matching DataFrame
  • Add QuarterEnd DateOffset (PR #321)
  • Add matrix multiplication function dot to DataFrame (GH #65)
  • Add orient option to Panel.from_dict to ease creation of mixed-type Panels (GH #359, #301)
  • Add DataFrame.from_dict with similar orient option
  • Can now pass list of tuples or list of lists to DataFrame.from_records for fast conversion to DataFrame (GH #357)
  • Can pass multiple levels to groupby, e.g. df.groupby(level=[0, 1]) (GH #103)
  • Can sort by multiple columns in DataFrame.sort_index (GH #92, PR #362)
  • Add fast get_value and put_value methods to DataFrame and micro-performance tweaks (GH #360)
  • Add cov instance methods to Series and DataFrame (GH #194, PR #362)
  • Add bar plot option to DataFrame.plot (PR #348)
  • Add idxmin and idxmax functions to Series and DataFrame for computing index labels achieving maximum and minimum values (PR #286)
  • Add read_clipboard function for parsing DataFrame from OS clipboard, should work across platforms (GH #300)
  • Add nunique function to Series for counting unique elements (GH #297)
  • DataFrame constructor will use Series name if no columns passed (GH #373)
  • Support regular expressions and longer delimiters in read_table/read_csv, but does not handle quoted strings yet (GH #364)
  • Add DataFrame.to_html for formatting DataFrame to HTML (PR #387)
  • MaskedArray can be passed to DataFrame constructor and masked values will be converted to NaN (PR #396)
  • Add DataFrame.boxplot function (GH #368, others)
  • Can pass extra args, kwds to DataFrame.apply (GH #376)

Improvements to existing features

  • Raise more helpful exception if date parsing fails in DateRange (GH #298)
  • Vastly improved performance of GroupBy on axes with a MultiIndex (GH #299)
  • Print level names in hierarchical index in Series repr (GH #305)
  • Return DataFrame when performing GroupBy on selected column and as_index=False (GH #308)
  • Can pass vector to on argument in DataFrame.join (GH #312)
  • Don't show Series name if it's None in the repr, also omit length for short Series (GH #317)
  • Show legend by default in DataFrame.plot, add legend boolean flag (GH #324)
  • Significantly improved performance of Series.order, which also makes np.unique called on a Series faster (GH #327)
  • Faster cythonized count by level in Series and DataFrame (GH #341)
  • Raise exception if dateutil 2.0 installed on Python 2.x runtime (GH #346)
  • Significant GroupBy performance enhancement with multiple keys with many "empty" combinations
  • New Cython vectorized function map_infer speeds up Series.apply and significantly when passed elementwise Python function, motivated by PR #355
  • Cythonized cache_readonly, resulting in substantial micro-performance enhancements throughout the codebase (GH #361)
  • Special Cython matrix iterator for applying arbitrary reduction operations with 3-5x better performance than np.apply_along_axis (GH #309)
  • Add raw option to DataFrame.apply for getting better performance when the passed function only requires an ndarray (GH #309)
  • Improve performance of MultiIndex.from_tuples
  • Can pass multiple levels to stack and unstack (GH #370)
  • Can pass multiple values columns to pivot_table (GH #381)
  • Can call DataFrame.delevel with standard Index with name set (GH #393)
  • Use Series name in GroupBy for result index (GH #363)
  • Refactor Series/DataFrame stat methods to use common set of NaN-friendly function
  • Handle NumPy scalar integers at C level in Cython conversion routines

Bug fixes

  • Fix bug in DataFrame.to_csv when writing a DataFrame with an index name (GH #290)
  • DataFrame should clear its Series caches on consolidation, was causing "stale" Series to be returned in some corner cases (GH #304)
  • DataFrame constructor failed if a column had a list of tuples (GH #293)
  • Ensure that Series.apply always returns a Series and implement Series.round (GH #314)
  • Support boolean columns in Cythonized groupby functions (GH #315)
  • DataFrame.describe should not fail if there are no numeric columns, instead return categorical describe (GH #323)
  • Fixed bug which could cause columns to be printed in wrong order in DataFrame.to_string if specific list of columns passed (GH #325)
  • Fix legend plotting failure if DataFrame columns are integers (GH #326)
  • Shift start date back by one month for Yahoo! Finance API in (GH #329)
  • Fix DataFrame.join failure on unconsolidated inputs (GH #331)
  • DataFrame.min/max will no longer fail on mixed-type DataFrame (GH #337)
  • Fix read_csv / read_table failure when passing list to index_col that is not in ascending order (GH #349)
  • Fix failure passing Int64Index to Index.union when both are monotonic
  • Fix error when passing SparseSeries to (dense) DataFrame constructor
  • Added missing bang at top of (GH #352)
  • Change is_monotonic on MultiIndex so it properly compares the tuples
  • Fix MultiIndex outer join logic (GH #351)
  • Set index name attribute with single-key groupby (GH #358)
  • Bug fix in reflexive binary addition in Series and DataFrame for non-commutative operations (like string concatenation) (GH #353)
  • will invoke Cython (GH #192)
  • Fix block consolidation bug after inserting column into MultiIndex (GH #366)
  • Fix bug in join operations between Index and Int64Index (GH #367)
  • Handle min_periods=0 case in moving window functions (GH #365)
  • Fixed corner cases in DataFrame.apply/pivot with empty DataFrame (GH #378)
  • Fixed repr exception when Series name is a tuple
  • Always return DateRange from asfreq (GH #390)
  • Pass level names to swaplavel (GH #379)
  • Don't lose index names in MultiIndex.droplevel (GH #394)
  • Infer more proper return type in DataFrame.apply when no columns or rows depending on whether the passed function is a reduction (GH #389)
  • Always return NA/NaN from Series.min/max and DataFrame.min/max when all of a row/column/values are NA (GH #384)
  • Enable partial setting with .ix / advanced indexing (GH #397)
  • Handle mixed-type DataFrames correctly in unstack, do not lose type information (GH #403)
  • Fix integer name formatting bug in Index.format and in Series.__repr__
  • Handle label types other than string passed to groupby (GH #405)
  • Fix bug in .ix-based indexing with partial retrieval when a label is not contained in a level
  • Index name was not being pickled (GH #408)
  • Level name should be passed to result index in GroupBy.apply (GH #416)


  • Craig Austin
  • Marius Cobzarenco
  • Joel Cross
  • Jeff Hammerbacher
  • Adam Klein
  • Thomas Kluyver
  • Jev Kuznetsov
  • Kieran O'Mahony
  • Wouter Overmeire
  • Nathan Pinger
  • Christian Prinoth
  • Skipper Seabold
  • Chang She
  • Ted Square
  • Aman Thakral
  • Chris Uga
  • Dieter Vandenbussche
  • carljv
  • rsamson

pandas 0.5.0

Release date: 10/24/2011

This release of pandas includes a number of API changes (see below) and cleanup of deprecated APIs from pre-0.4.0 releases. There are also bug fixes, new features, numerous significant performance enhancements, and includes a new IPython completer hook to enable tab completion of DataFrame columns accesses as attributes (a new feature).

In addition to the changes listed here from 0.4.3 to 0.5.0, the minor releases 0.4.1, 0.4.2, and 0.4.3 brought some significant new functionality and performance improvements that are worth taking a look at.

Thanks to all for bug reports, contributed patches and generally providing feedback on the library.

API Changes

  • read_table, read_csv, and ExcelFile.parse default arguments for index_col is now None. To use one or more of the columns as the resulting DataFrame's index, these must be explicitly specified now
  • Parsing functions like read_csv no longer parse dates by default (GH #225)
  • Removed weights option in panel regression which was not doing anything principled (GH #155)
  • Changed buffer argument name in Series.to_string to buf
  • Series.to_string and DataFrame.to_string now return strings by default instead of printing to sys.stdout
  • Deprecated nanRep argument in various to_string and to_csv functions in favor of na_rep. Will be removed in 0.6 (GH #275)
  • Renamed delimiter to sep in DataFrame.from_csv for consistency
  • Changed order of Series.clip arguments to match those of numpy.clip and added (unimplemented) out argument so numpy.clip can be called on a Series (GH #272)
  • Series functions renamed (and thus deprecated) in 0.4 series have been removed:
    • asOf, use asof
    • toDict, use to_dict
    • toString, use to_string
    • toCSV, use to_csv
    • merge, use map
    • applymap, use apply
    • combineFirst, use combine_first
    • _firstTimeWithValue use first_valid_index
    • _lastTimeWithValue use last_valid_index
  • DataFrame functions renamed / deprecated in 0.4 series have been removed:
    • asMatrix method, use as_matrix or values attribute
    • combineFirst, use combine_first
    • getXS, use xs
    • merge, use join
    • fromRecords, use from_records
    • fromcsv, use from_csv
    • toRecords, use to_records
    • toDict, use to_dict
    • toString, use to_string
    • toCSV, use to_csv
    • _firstTimeWithValue use first_valid_index
    • _lastTimeWithValue use last_valid_index
    • toDataMatrix is no longer needed
    • rows() method, use index attribute
    • cols() method, use columns attribute
    • dropEmptyRows(), use dropna(how='all')
    • dropIncompleteRows(), use dropna()
    • tapply(f), use apply(f, axis=1)
    • tgroupby(keyfunc, aggfunc), use groupby with axis=1
  • Other outstanding deprecations have been removed:
    • indexField argument in DataFrame.from_records
    • missingAtEnd argument in Series.order. Use na_last instead
    • Series.fromValue classmethod, use regular Series constructor instead
    • Functions parseCSV, parseText, and parseExcel methods in have been removed
    • Index.asOfDate function
    • Panel.getMinorXS (use minor_xs) and Panel.getMajorXS (use major_xs)
    • Panel.toWide, use Panel.to_wide instead

New features / modules

  • 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
  • Add 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
  • Added column attribute access to DataFrame, e.g. df.A equivalent to df['A'] if 'A' is a column in the DataFrame (PR #213)
  • Added IPython tab completion hook for DataFrame columns. (PR #233, GH #230)
  • Implement Series.describe for Series containing objects (PR #241)
  • Add inner join option to DataFrame.join when joining on key(s) (GH #248)
  • Can select set of DataFrame columns by passing a list to __getitem__ (GH #253)
  • Can use & and | to intersection / 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
  • Implemented Panel.take
  • Add set_eng_float_format function for setting alternate DataFrame floating point string formatting
  • Add convenience set_index function for creating a DataFrame index from its existing columns

Improvements to existing features

  • Major performance improvements in file parsing functions read_csv and read_table
  • Added Cython function for converting tuples to ndarray very fast. Speeds up many MultiIndex-related operations
  • File parsing functions like read_csv and read_table will explicitly check if a parsed index has duplicates and raise a more helpful exception rather than deferring the check until later
  • 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)
  • Improved speed of DataFrame.xs on mixed-type DataFrame objects by about 5x, regression from 0.3.0 (GH #215)
  • With new DataFrame.align method, speeding up binary operations between differently-indexed DataFrame objects by 10-25%.
  • Significantly sped up conversion of nested dict into DataFrame (GH #212)
  • Can pass hierarchical index level name to groupby instead of the level number if desired (GH #223)
  • Add support for different delimiters in DataFrame.to_csv (PR #244)
  • Add more helpful error message when importing pandas post-installation from the source directory (GH #250)
  • Significantly speed up DataFrame __repr__ and count on large mixed-type DataFrame objects
  • Better handling of pyx file dependencies in Cython module build (GH #271)

Bug fixes

  • read_csv / read_table fixes - Be less aggressive about converting float->int in cases of floating point

    representations of integers like 1.0, 2.0, etc.

    • "True"/"False" will not get correctly converted to boolean
    • Index name attribute will get set when specifying an index column
    • Passing column names should force header=None (GH #257)
    • Don't modify passed column names when index_col is not None (GH #258)
    • Can sniff CSV separator in zip file (since seek is not supported, was failing before)
  • Worked around matplotlib "bug" in which series[:, np.newaxis] fails. Should be reported upstream to matplotlib (GH #224)

  • DataFrame.iteritems was not returning Series with the name attribute set. Also neither was DataFrame._series

  • Can store objects in HDFStore (GH #231)

  • Index and Series names are now stored in HDFStore

  • Fixed problem in which data would get upcasted to object dtype in GroupBy.apply operations (GH #237)

  • Fixed outer join bug with empty DataFrame (GH #238)

  • Can create empty Panel (GH #239)

  • Fix join on single key when passing list with 1 entry (GH #246)

  • Don't raise Exception on plotting DataFrame with an all-NA column (GH #251, PR #254)

  • Bug min/max errors when called on integer DataFrames (PR #241)

  • DataFrame.iteritems and DataFrame._series not assigning name attribute

  • Panel.__repr__ raised exception on length-0 major/minor axes

  • DataFrame.join on key with empty DataFrame produced incorrect columns

  • Implemented MultiIndex.diff (GH #260)

  • Int64Index.take and MultiIndex.take lost name field, fix downstream issue GH #262

  • Can pass list of tuples to Series (GH #270)

  • Can pass level name to DataFrame.stack

  • Support set operations between MultiIndex and Index

  • Fix many corner cases in MultiIndex set operations - Fix MultiIndex-handling bug with GroupBy.apply when returned groups are not indexed the same

  • Fix corner case bugs in DataFrame.apply

  • Setting DataFrame index did not cause Series cache to get cleared

  • Various int32 -> int64 platform-specific issues

  • Don't be too aggressive converting to integer when parsing file with MultiIndex (GH #285)

  • Fix bug when slicing Series with negative indices before beginning


  • Thomas Kluyver
  • Daniel Fortunov
  • Aman Thakral
  • Luca Beltrame
  • Wouter Overmeire

pandas 0.4.3

Release notes

Release date: 10/9/2011

This is largely a bugfix release from 0.4.2 but also includes a handful of new and enhanced features. Also, pandas can now be installed and used on Python 3 (thanks Thomas Kluyver!).

New features / modules

  • Python 3 support using 2to3 (PR #200, Thomas Kluyver)
  • Add name attribute to Series and added relevant logic and tests. Name now prints as part of Series.__repr__
  • Add name attribute to standard Index so that stacking / unstacking does not discard names and so that indexed DataFrame objects can be reliably round-tripped to flat files, pickle, HDF5, etc.
  • Add isnull and notnull as instance methods on Series (PR #209, GH #203)

Improvements to existing features

  • Skip xlrd-related unit tests if not installed
  • Index.append and MultiIndex.append can accept a list of Index objects to concatenate together
  • 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 (GH #205)
  • Refactored Series.__repr__ to be a bit more clean and consistent

API Changes

  • Series.describe and DataFrame.describe now bring the 25% and 75% quartiles instead of the 10% and 90% deciles. The other outputs have not changed
  • Series.toString will print deprecation warning, has been de-camelCased to to_string

Bug fixes

  • Fix broken interaction between Index and Int64Index when calling intersection. Implement Int64Index.intersection
  • MultiIndex.sortlevel discarded the level names (GH #202)
  • Fix bugs in groupby, join, and append due to improper concatenation of MultiIndex objects (GH #201)
  • Fix regression from 0.4.1, isnull and notnull ceased to work on other kinds of Python scalar objects like datetime.datetime
  • Raise more helpful exception when attempting to write empty DataFrame or LongPanel to HDFStore (GH #204)
  • Use stdlib csv module to properly escape strings with commas in DataFrame.to_csv (PR #206, Thomas Kluyver)
  • Fix Python ndarray access in Cython code for sparse blocked index integrity check
  • Fix bug writing Series to CSV in Python 3 (PR #209)
  • Miscellaneous Python 3 bugfixes


  • Thomas Kluyver
  • rsamson

pandas 0.4.2

Release notes

Release date: 10/3/2011

This is a performance optimization release with several bug fixes. The new Int64Index and new merging / joining Cython code and related Python infrastructure are the main new additions

New features / modules

  • Added fast Int64Index type with specialized join, union, intersection. Will result in significant performance enhancements for int64-based time series (e.g. using NumPy's datetime64 one day) and also faster operations on DataFrame objects storing record array-like data.
  • Refactored Index classes to have a join method and associated data alignment routines throughout the codebase to be able to leverage optimized joining / merging routines.
  • Added Series.align method for aligning two series with choice of join method
  • Wrote faster Cython data alignment / merging routines resulting in substantial speed increases
  • Added is_monotonic property to Index classes with associated Cython code to evaluate the monotonicity of the Index values
  • Add method get_level_values to MultiIndex
  • Implemented shallow copy of BlockManager object in DataFrame internals

Improvements to existing features

  • Improved performance of isnull and notnull, a regression from v0.3.0 (GH #187)
  • Wrote templating / code generation script to auto-generate Cython code for various functions which need to be available for the 4 major data types used in pandas (float64, bool, object, int64)
  • 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 (GH #176)
  • Substantially improved performance of generic Index.intersection and Index.union
  • Improved performance of DateRange.union with overlapping ranges and non-cacheable offsets (like Minute). Implemented analogous fast DateRange.intersection for overlapping ranges.
  • Implemented BlockManager.take resulting in significantly faster take performance on mixed-type DataFrame objects (GH #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
  • Added informative Exception when passing dict to DataFrame groupby aggregation with axis != 0

API Changes


Bug fixes

  • Fixed minor unhandled exception in Cython code implementing fast groupby aggregation operations
  • Fixed bug in unstacking code manifesting with more than 3 hierarchical levels
  • Throw exception when step specified in label-based slice (GH #185)
  • Fix isnull to correctly work with np.float32. Fix upstream bug described in GH #182
  • Finish implementation of as_index=False in groupby for DataFrame aggregation (GH #181)
  • Raise SkipTest for pre-epoch HDFStore failure. Real fix will be sorted out via datetime64 dtype


  • Uri Laserson
  • Scott Sinclair

pandas 0.4.1

Release notes

Release date: 9/25/2011

This is primarily a bug fix release but includes some new features and improvements

New features / modules

  • Added new DataFrame methods get_dtype_counts and property dtypes
  • Setting of values using .ix indexing attribute in mixed-type DataFrame objects has been implemented (fixes GH #135)
  • read_csv can read multiple columns into a MultiIndex. DataFrame's to_csv method will properly write out a MultiIndex which can be read back (PR #151, thanks to Skipper Seabold)
  • Wrote fast time series merging / joining methods in Cython. Will be integrated later into DataFrame.join and related functions
  • Added ignore_index option to DataFrame.append for combining unindexed records stored in a DataFrame

Improvements to existing features

  • Some speed enhancements with internal Index type-checking function
  • DataFrame.rename has a new copy parameter which can rename a DataFrame in place
  • Enable unstacking by level name (PR #142)
  • Enable sortlevel to work by level name (PR #141)
  • read_csv can automatically "sniff" other kinds of delimiters using csv.Sniffer (PR #146)
  • Improved speed of unit test suite by about 40%
  • Exception will not be raised calling HDFStore.remove on non-existent node with where clause
  • Optimized _ensure_index function resulting in performance savings in type-checking Index objects

API Changes


Bug fixes

  • Fixed DataFrame constructor bug causing downstream problems (e.g. .copy() failing) when passing a Series as the values along with a column name and index
  • Fixed single-key groupby on DataFrame with as_index=False (GH #160)
  • Series.shift was failing on integer Series (GH #154)
  • unstack methods were producing incorrect output in the case of duplicate hierarchical labels. An exception will now be raised (GH #147)
  • Calling count with level argument caused reduceat failure or segfault in earlier NumPy (GH #169)
  • Fixed DataFrame.corrwith to automatically exclude non-numeric data (GH #144)
  • Unicode handling bug fixes in DataFrame.to_string (GH #138)
  • Excluding OLS degenerate unit test case that was causing platform specific failure (GH #149)
  • Skip blosc-dependent unit tests for PyTables < 2.2 (PR #137)
  • Calling copy on DateRange did not copy over attributes to the new object (GH #168)
  • Fix bug in HDFStore in which Panel data could be appended to a Table with different item order, thus resulting in an incorrect result read back


  • Yaroslav Halchenko
  • Jeff Reback
  • Skipper Seabold
  • Dan Lovell
  • Nick Pentreath

pandas 0.4.0

Release notes

Release date: 9/12/2011

New features / modules

  • pandas.core.sparse module: "Sparse" (mostly-NA, or some other fill value) versions of Series, DataFrame, and Panel. For low-density data, this will result in significant performance boosts, and smaller memory footprint. Added to_sparse methods to Series, DataFrame, and Panel. See online documentation for more on these
  • Fancy indexing operator on Series / DataFrame, e.g. via .ix operator. Both getting and setting of values is supported; however, setting values will only currently work on homogeneously-typed DataFrame objects. Things like:
    • series.ix[[d1, d2, d3]]
    • frame.ix[5:10, ['C', 'B', 'A']], frame.ix[5:10, 'A':'C']
    • frame.ix[date1:date2]
  • Significantly enhanced groupby functionality
    • Can groupby multiple keys, e.g. df.groupby(['key1', 'key2']). Iteration with multiple groupings products a flattened tuple
    • "Nuisance" columns (non-aggregatable) will automatically be excluded from DataFrame aggregation operations
    • Added automatic "dispatching to Series / DataFrame methods to more easily invoke methods on groups. e.g. s.groupby(crit).std() will work even though std is not implemented on the GroupBy class
  • Hierarchical / multi-level indexing
    • New the MultiIndex class. Integrated MultiIndex into Series and DataFrame fancy indexing, slicing, __getitem__ and __setitem, reindexing, etc. Added level keyword argument to groupby to enable grouping by a level of a MultiIndex
  • New data reshaping functions: stack and unstack on DataFrame and Series
    • Integrate with MultiIndex to enable sophisticated reshaping of data
  • Index objects (labels for axes) are now capable of holding tuples
  • Series.describe, DataFrame.describe: produces an R-like table of summary statistics about each data column
  • DataFrame.quantile, Series.quantile for computing sample quantiles of data across requested axis
  • Added general DataFrame.dropna method to replace dropIncompleteRows and dropEmptyRows, deprecated those.
  • Series arithmetic methods with optional fill_value for missing data, e.g. a.add(b, fill_value=0). If a location is missing for both it will still be missing in the result though.
  • fill_value option has been added to DataFrame.{add, mul, sub, div} methods similar to Series
  • Boolean indexing with DataFrame objects: data[data > 0.1] = 0.1 or data[data> other] = 1.
  • pytz / tzinfo support in DateRange
    • tz_localize, tz_normalize, and tz_validate methods added
  • Added ExcelFile class to for parsing multiple sheets out of a single Excel 2003 document
  • GroupBy aggregations can now optionally broadcast, e.g. produce an object of the same size with the aggregated value propagated
  • Added select function in all data structures: reindex axis based on arbitrary criterion (function returning boolean value), e.g. x: 'foo' in x, axis=1)
  • DataFrame.consolidate method, API function relating to redesigned internals
  • DataFrame.insert method for inserting column at a specified location rather than the default __setitem__ behavior (which puts it at the end)
  • HDFStore class in has been largely rewritten using patches from Jeff Reback from others. It now supports mixed-type DataFrame and Series data and can store Panel objects. It also has the option to query DataFrame and Panel data. Loading data from legacy HDFStore files is supported explicitly in the code
  • Added set_printoptions method to modify appearance of DataFrame tabular output
  • rolling_quantile functions; a moving version of Series.quantile / DataFrame.quantile
  • Generic rolling_apply moving window function
  • New drop method added to Series, DataFrame, etc. which can drop a set of labels from an axis, producing a new object
  • reindex methods now sport a copy option so that data is not forced to be copied then the resulting object is indexed the same
  • Added sort_index methods to Series and Panel. Renamed DataFrame.sort to sort_index. Leaving DataFrame.sort for now.
  • Added skipna option to statistical instance methods on all the data structures
  • module providing a consistent interface for reading time series data from several different sources

Improvements to existing features

  • The 2-dimensional DataFrame and DataMatrix classes have been extensively redesigned internally into a single class DataFrame, preserving where possible their optimal performance characteristics. This should reduce confusion from users about which class to use.
    • Note that under the hood there is a new essentially "lazy evaluation" scheme within respect to adding columns to DataFrame. During some operations, like-typed blocks will be "consolidated" but not before.
  • DataFrame accessing columns repeatedly is now significantly faster than DataMatrix used to be in 0.3.0 due to an internal Series caching mechanism (which are all views on the underlying data)
  • Column ordering for mixed type data is now completely consistent in DataFrame. In prior releases, there was inconsistent column ordering in DataMatrix
  • Improved console / string formatting of DataMatrix with negative numbers
  • Improved tabular data parsing functions, read_table and read_csv:
    • Added skiprows and na_values arguments to functions for more flexible IO
    • parseCSV / read_csv functions and others in now can take a list of custom NA values, and also a list of rows to skip
  • Can slice DataFrame and get a view of the data (when homogeneously typed), e.g. frame.xs(idx, copy=False) or frame.ix[idx]
  • Many speed optimizations throughout Series and DataFrame
  • Eager evaluation of groups when calling groupby functions, so if there is an exception with the grouping function it will raised immediately versus sometime later on when the groups are needed
  • datetools.WeekOfMonth offset can be parameterized with n different than 1 or -1.
  • Statistical methods on DataFrame like mean, std, var, skew will now ignore non-numerical data. Before a not very useful error message was generated. A flag numeric_only has been added to DataFrame.sum and DataFrame.count to enable this behavior in those methods if so desired (disabled by default)
  • DataFrame.pivot generalized to enable pivoting multiple columns into a DataFrame with hierarchical columns
  • DataFrame constructor can accept structured / record arrays
  • Panel constructor can accept a dict of DataFrame-like objects. Do not need to use from_dict anymore (from_dict is there to stay, though).

API Changes

  • The DataMatrix variable now refers to DataFrame, will be removed within two releases
  • WidePanel is now known as Panel. The WidePanel variable in the pandas namespace now refers to the renamed Panel class
  • LongPanel and Panel / WidePanel now no longer have a common subclass. LongPanel is now a subclass of DataFrame having a number of additional methods and a hierarchical index instead of the old LongPanelIndex object, which has been removed. Legacy LongPanel pickles may not load properly
  • Cython is now required to build pandas from a development branch. This was done to avoid continuing to check in cythonized C files into source control. Builds from released source distributions will not require Cython
  • Cython code has been moved up to a top level pandas/src directory. Cython extension modules have been renamed and promoted from the lib subpackage to the top level, i.e.
    • pandas.lib.tseries -> pandas._tseries
    • pandas.lib.sparse -> pandas._sparse
  • DataFrame pickling format has changed. Backwards compatibility for legacy pickles is provided, but it's recommended to consider PyTables-based HDFStore for storing data with a longer expected shelf life
  • A copy argument has been added to the DataFrame constructor to avoid unnecessary copying of data. Data is no longer copied by default when passed into the constructor
  • Handling of boolean dtype in DataFrame has been improved to support storage of boolean data with NA / NaN values. Before it was being converted to float64 so this should not (in theory) cause API breakage
  • To optimize performance, Index objects now only check that their labels are unique when uniqueness matters (i.e. when someone goes to perform a lookup). This is a potentially dangerous tradeoff, but will lead to much better performance in many places (like groupby).
  • Boolean indexing using Series must now have the same indices (labels)
  • Backwards compatibility support for begin/end/nPeriods keyword arguments in DateRange class has been removed
  • More intuitive / shorter filling aliases ffill (for pad) and bfill (for backfill) have been added to the functions that use them: reindex, asfreq, fillna.
  • pandas.core.mixins code moved to pandas.core.generic
  • buffer keyword arguments (e.g. DataFrame.toString) renamed to buf to avoid using Python built-in name
  • DataFrame.rows() removed (use DataFrame.index)
  • Added deprecation warning to DataFrame.cols(), to be removed in next release
  • DataFrame deprecations and de-camelCasing: merge, asMatrix, toDataMatrix, _firstTimeWithValue, _lastTimeWithValue, toRecords, fromRecords, tgroupby, toString
  • method deprecations
    • parseCSV is now read_csv and keyword arguments have been de-camelCased
    • parseText is now read_table
    • parseExcel is replaced by the ExcelFile class and its parse method
  • fillMethod arguments (deprecated in prior release) removed, should be replaced with method
  • Series.fill, DataFrame.fill, and Panel.fill removed, use fillna instead
  • groupby functions now exclude NA / NaN values from the list of groups. This matches R behavior with NAs in factors e.g. with the tapply function
  • Removed parseText, parseCSV and parseExcel from pandas namespace
  • Series.combineFunc renamed to Series.combine and made a bit more general with a fill_value keyword argument defaulting to NaN
  • Removed pandas.core.pytools module. Code has been moved to pandas.core.common
  • Tacked on groupName attribute for groups in GroupBy renamed to name
  • Panel/LongPanel dims attribute renamed to shape to be more conformant
  • Slicing a Series returns a view now
  • More Series deprecations / renaming: toCSV to to_csv, asOf to asof, merge to map, applymap to apply, toDict to to_dict, combineFirst to combine_first. Will print FutureWarning.
  • DataFrame.to_csv does not write an "index" column label by default anymore since the output file can be read back without it. However, there is a new index_label argument. So you can do index_label='index' to emulate the old behavior
  • datetools.Week argument renamed from dayOfWeek to weekday
  • timeRule argument in shift has been deprecated in favor of using the offset argument for everything. So you can still pass a time rule string to offset
  • Added optional encoding argument to read_csv, read_table, to_csv, from_csv to handle unicode in python 2.x

Bug fixes

  • Column ordering in will match CSV in the presence of mixed-type data
  • Fixed handling of Excel 2003 dates in
  • DateRange caching was happening with high resolution DateOffset objects, e.g. DateOffset(seconds=1). This has been fixed
  • Fixed __truediv__ issue in DataFrame
  • Fixed DataFrame.toCSV bug preventing IO round trips in some cases
  • Fixed bug in Series.plot causing matplotlib to barf in exceptional cases
  • Disabled Index objects from being hashable, like ndarrays
  • Added __ne__ implementation to Index so that operations like ts[ts != idx] will work
  • Added __ne__ implementation to DataFrame
  • Bug / unintuitive result when calling fillna on unordered labels
  • Bug calling sum on boolean DataFrame
  • Bug fix when creating a DataFrame from a dict with scalar values
  • Series.{sum, mean, std, ...} now return NA/NaN when the whole Series is NA
  • NumPy 1.4 through 1.6 compatibility fixes
  • Fixed bug in bias correction in rolling_cov, was affecting rolling_corr too
  • R-square value was incorrect in the presence of fixed and time effects in the PanelOLS classes
  • HDFStore can handle duplicates in table format, will take


  • Joon Ro
  • Michael Pennington
  • Chris Uga
  • Chris Withers
  • Jeff Reback
  • Ted Square
  • Craig Austin
  • William Ferreira
  • Daniel Fortunov
  • Tony Roberts
  • Martin Felder
  • John Marino
  • Tim McNamara
  • Justin Berka
  • Dieter Vandenbussche
  • Shane Conway
  • Skipper Seabold
  • Chris Jordan-Squire

pandas 0.3.0

Release notes

Release date: February 20, 2011

New features / modules

  • corrwith function to compute column- or row-wise correlations between two

    DataFrame objects

  • Can boolean-index DataFrame objects, e.g. df[df > 2] = 2, px[px > last_px] = 0

  • Added comparison magic methods (__lt__, __gt__, etc.)

  • Flexible explicit arithmetic methods (add, mul, sub, div, etc.)

  • Added reindex_like method

  • Added reindex_like method to WidePanel

  • Convenience functions for accessing SQL-like databases in


  • Added (still experimental) HDFStore class for storing pandas data

    structures using HDF5 / PyTables in module

  • Added WeekOfMonth date offset

  • pandas.rpy (experimental) module created, provide some interfacing /

conversion between rpy2 and pandas


  • Unit test coverage: 100% line coverage of core data structures

  • Speed enhancement to rolling_{median, max, min}

  • Column ordering between DataFrame and DataMatrix is now consistent: before

    DataFrame would not respect column order

  • Improved {Series, DataFrame}.plot methods to be more flexible (can pass

    matplotlib Axis arguments, plot DataFrame columns in multiple subplots, etc.)

API Changes

  • Exponentially-weighted moment functions in pandas.stats.moments have a

    more consistent API and accept a min_periods argument like their regular moving counterparts.

  • fillMethod argument in Series, DataFrame changed to method,

    FutureWarning added.

  • fill method in Series, DataFrame/DataMatrix, WidePanel renamed to

    fillna, FutureWarning added to fill

  • Renamed DataFrame.getXS to xs, FutureWarning added

  • Removed cap and floor functions from DataFrame, renamed to

    clip_upper and clip_lower for consistency with NumPy

Bug fixes

  • Fixed bug in IndexableSkiplist Cython code that was breaking

    rolling_max function

  • Numerous numpy.int64-related indexing fixes

  • Several NumPy 1.4.0 NaN-handling fixes

  • Bug fixes to

  • Fixed DateRange caching issue with unusual date offsets

  • Fixed bug in DateRange.union

  • Fixed corner case in IndexableSkiplist implementation

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