Version History


  • New itertools:
  • Improvements to existing itertools:
    • A few itertools are now slightly faster due to some function optimizations. (Thanks to MSeifert04)
  • The docs have been substantially revised with installation notes, categories for library functions, links, and more. (Thanks to pylang)


  • Removed itertools:
    • context has been removed due to a design flaw - see below for replacement options. (thanks to NeilGirdhar)
  • Improvements to existing itertools:
    • side_effect now supports before and after keyword arguments. (Thanks to yardsale8)
  • PyPy and PyPy3 are now supported.

The major version change is due to the removal of the context function. Replace it with standard with statement context management:

# Don't use context() anymore
file_obj = StringIO()
consume(print(x, file=f) for f in context(file_obj) for x in u'123')

# Use a with statement instead
file_obj = StringIO()
with file_obj as f:
    consume(print(x, file=f) for x in u'123')


  • New itertools:
    • adjacent and groupby_transform (Thanks to diazona)
    • always_iterable (Thanks to jaraco)
    • (Removed in 3.0.0) context (Thanks to yardsale8)
    • divide (Thanks to mozbhearsum)
  • Improvements to existing itertools:
    • ilen is now slightly faster. (Thanks to wbolster)
    • peekable can now prepend items to an iterable. (Thanks to diazona)


  • New itertools:
    • distribute (Thanks to mozbhearsum and coady)
    • sort_together (Thanks to clintval)
    • stagger and zip_offset (Thanks to joshbode)
    • padded
  • Improvements to existing itertools:
    • peekable now handles negative indexes and slices with negative components properly.
    • intersperse is now slightly faster. (Thanks to pylang)
    • windowed now accepts a step keyword argument. (Thanks to pylang)
  • Python 3.6 is now supported.


  • Move docs 100% to


  • New itertools:
    • accumulate, all_equal, first_true, partition, and tail from the itertools documentation.
    • bucket (Thanks to Rosuav and cvrebert)
    • collapse (Thanks to abarnet)
    • interleave and interleave_longest (Thanks to abarnet)
    • side_effect (Thanks to nvie)
    • sliced (Thanks to j4mie and coady)
    • split_before and split_after (Thanks to astronouth7303)
    • spy (Thanks to themiurgo and mathieulongtin)
  • Improvements to existing itertools:
    • chunked is now simpler and more friendly to garbage collection. (Contributed by coady, with thanks to piskvorky)
    • collate now delegates to heapq.merge when possible. (Thanks to kmike and julianpistorius)
    • peekable-wrapped iterables are now indexable and sliceable. Iterating through peekable-wrapped iterables is also faster.
    • one and unique_to_each have been simplified. (Thanks to coady)


  • Added one from jaraco.util.itertools. (Thanks, jaraco!)
  • Added distinct_permutations and unique_to_each. (Contributed by bbayles)
  • Added windowed. (Contributed by bbayles, with thanks to buchanae, jaraco, and abarnert)
  • Simplified the implementation of chunked. (Thanks, nvie!)
  • Python 3.5 is now supported. Python 2.6 is no longer supported.
  • Python 3 is now supported directly; there is no 2to3 step.


  • Added iterate and with_iter. (Thanks, abarnert!)


  • Added (tested!) implementations of the recipes from the itertools documentation. (Thanks, Chris Lonnen!)
  • Added ilen. (Thanks for the inspiration, Matt Basta!)


  • chunked now returns lists rather than tuples. After all, they’re homogeneous. This slightly backward-incompatible change is the reason for the major version bump.
  • Added @consumer.
  • Improved test machinery.


  • Added first function.
  • Added Python 3 support.
  • Added a default arg to peekable.peek().
  • Noted how to easily test whether a peekable iterator is exhausted.
  • Rewrote documentation.


  • Initial release, with collate, peekable, and chunked. Could really use better docs.