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More routines for operating on iterables, beyond itertools

Project description

Python’s itertools library is a gem - you can compose elegant solutions for a variety of problems with the functions it provides. In more-itertools we collect additional building blocks, recipes, and routines for working with Python iterables.

Grouping chunked, sliced, distribute, divide, split_at, split_before, split_after, bucket, grouper, partition
Lookahead and lookback spy, peekable, seekable
Windowing windowed, stagger, pairwise
Augmenting count_cycle, intersperse, padded, adjacent, groupby_transform, padnone, ncycles
Combining collapse, sort_together, interleave, interleave_longest, collate, zip_offset, dotproduct, flatten, roundrobin, prepend
Summarizing ilen, first, last, one, unique_to_each, locate, rlocate, consecutive_groups, exactly_n, run_length, map_reduce, all_equal, first_true, nth, quantify
Selecting islice_extended, strip, lstrip, rstrip, take, tail, unique_everseen, unique_justseen
Combinatorics distinct_permutations, circular_shifts, powerset, random_product, random_permutation, random_combination, random_combination_with_replacement, nth_combination
Wrapping always_iterable, consumer, with_iter, iter_except
Others replace, numeric_range, always_reversible, side_effect, iterate, difference, make_decorator, SequenceView, consume, accumulate, tabulate, repeatfunc

Getting started

To get started, install the library with pip:

pip install more-itertools

The recipes from the itertools docs are included in the top-level package:

>>> from more_itertools import flatten
>>> iterable = [(0, 1), (2, 3)]
>>> list(flatten(iterable))
[0, 1, 2, 3]

Several new recipes are available as well:

>>> from more_itertools import chunked
>>> iterable = [0, 1, 2, 3, 4, 5, 6, 7, 8]
>>> list(chunked(iterable, 3))
[[0, 1, 2], [3, 4, 5], [6, 7, 8]]

>>> from more_itertools import spy
>>> iterable = (x * x for x in range(1, 6))
>>> head, iterable = spy(iterable, n=3)
>>> list(head)
[1, 4, 9]
>>> list(iterable)
[1, 4, 9, 16, 25]

For the full listing of functions, see the API documentation.


more-itertools is maintained by @erikrose and @bbayles, with help from many others. If you have a problem or suggestion, please file a bug or pull request in this repository. Thanks for contributing!

Version History


  • New itertools:
    • last (thanks to tmshn)
    • replace (thanks to pylang)
    • rlocate (thanks to jferard and pylang)
  • Improvements to existing itertools:
    • locate can now search for multiple items
  • Other changes:
    • The docs now include a nice table of tools (thanks MSeifert04)


  • New itertools:
  • Improvements to existing itertools:
    • bucket now complies with PEP 479 (thanks to irmen)
  • Other changes:
    • Python 3.7 is now supported (thanks to irmen)
    • Python 3.3 is no longer supported
    • The test suite no longer requires third-party modules to run
    • The API docs now include links to source code


  • New itertools:
    • split_at (thanks to michael-celani)
    • circular_shifts (thanks to hiqua)
    • make_decorator - see the blog post Yo, I heard you like decorators for a tour (thanks to pylang)
    • always_reversible (thanks to michael-celani)
    • nth_combination (from the Python 3.7 docs)
  • Improvements to existing itertools:
    • seekable now has an elements method to return cached items.
    • The performance tradeoffs between roundrobin and interleave_longest are now documented (thanks michael-celani, pylang, and MSeifert04)


  • No code changes - this release fixes how the docs display on PyPI.


  • New itertools:
    • consecutive_groups (Based on the example in the Python 2.4 docs)
    • seekable (If you’re looking for how to “reset” an iterator, you’re in luck!)
    • exactly_n (thanks to michael-celani)
    • run_length.encode and run_length.decode
    • difference
  • Improvements to existing itertools:
    • The number of items between filler elements in intersperse can now be specified (thanks to pylang)
    • distinct_permutations and peekable got some minor adjustments (thanks to MSeifert04)
    • always_iterable now returns an iterator object. It also now allows different types to be considered iterable (thanks to jaraco)
    • bucket can now limit the keys it stores in memory
    • one now allows for custom exceptions (thanks to kalekundert)
  • Other changes:
    • A few typos were fixed (thanks to EdwardBetts)
    • All tests can now be run with python test

The major version update is due to the change in the return value of always_iterable. It now always returns iterator objects:

>>> from more_itertools import always_iterable
# Non-iterable objects are wrapped with iter(tuple(obj))
>>> always_iterable(12345)
<tuple_iterator object at 0x7fb24c9488d0>
>>> list(always_iterable(12345))
# Iterable objects are wrapped with iter()
>>> always_iterable([1, 2, 3, 4, 5])
<list_iterator object at 0x7fb24c948c50>


  • New itertools:
    • lstrip, rstrip, and strip (thanks to MSeifert04 and pylang)
    • islice_extended
  • Improvements to existing itertools:
    • Some bugs with slicing peekable-wrapped iterables were fixed


  • New itertools:
    • numeric_range (Thanks to BebeSparkelSparkel and MSeifert04)
    • count_cycle (Thanks to BebeSparkelSparkel)
    • locate (Thanks to pylang and MSeifert04)
  • 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.

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