Version History

More routines for operating on iterables, beyond itertools




  • New functions
  • Changes to existing functions
    • zip_broadcast() was improved (thanks to kalekundert and pochmann)

    • consume() had its type annotation fixed (thanks to obaltian)

  • Other changes
    • Some documentation and testing issues were fixed (thanks to OlegAlexander)



  • New functions
  • Changes to existing functions
    • sieve() was updated to match the Python itertools docs

    • maxsplit() was updated to fix a bug (thanks to abingham)

    • sliced() had its type hint updated (thanks to ad-chaos)

  • Other changes
    • The batched function is marked as deprecated and will be removed in a future major release. For Python 3.12 and above, use itertools.batched instead. (thanks to neutrinoceros)

    • The type hints now used postponed evaluation of annotations from PEP 563 (thanks to Isira-Seneviratne)

    • Some documentation issues were fixed (thanks to Voskov and jdkandersson)


  • Potentially breaking changes
    • grouper() no longer accepts an integer as its first argument. Previously this raised a DeprecationWarning.

    • collate() has been removed. Use the built-in heapq.merge() instead.

    • windowed() now yields nothing when its iterable is empty.

    • This library now advertises support for Python 3.7+.

  • New functions
  • Other changes
    • Some documentation issues were fixed (thanks to nanouasyn)


  • New functions
  • Changes to existing functions
    • concurrent.futures.ThreadPoolExecutor is now imported lazily in callback_iter().

    • tail() is now optimized for iterables with a fixed length.

  • Other changes
    • Some documentation issues were fixed (thanks to pochmann and timgates42)

    • This library is now marked for Python 3.10 compatibility in PyPI (thanks to chayim)


  • New functions
    • The subslices() recipe from the itertools docs was added (thanks to rhettinger)

  • Changes to existing functions
    • The ichunked() function is now more efficient (thanks to hjtran0 and seanmacavaney)

    • The difference() function is now more efficient (thanks to Masynchin)

    • The grouper() recipe now has more features, mirroring the one in the itertools docs (thanks to rhettinger)

  • Other changes
    • Some documentation issues were fixed (thanks to medvied and Freed-Wu)

    • The more_itertools package is now built with flit (thanks to mgorny)


  • Bug fixes
    • Some documentation issues were fixed (thanks to Masynchin, spookylukey, astrojuanlu, and stephengmatthews)

    • Python 3.5 support was temporarily restored (thanks to mattbonnell)



  • Changes to existing functions
    • The type stub for iter_except() was improved (thanks to MarcinKonowalczyk)

  • Other changes:
    • Type stubs now ship with the source release (thanks to saaketp)

    • The Sphinx docs were improved (thanks to MarcinKonowalczyk)



  • New functions
  • Changes to existing functions


  • New functions
  • Changes to existing functions
    • distinct_combinations() now uses a non-recursive algorithm (thanks to knutdrand)

    • pad_none() is now the preferred name for padnone(), though the latter remains available.

    • pairwise() will now use the Python standard library implementation on Python 3.10+

    • sort_together() now accepts a key argument (thanks to brianmaissy)

    • seekable() now has a peek method, and can indicate whether the iterator it’s wrapping is exhausted (thanks to gsakkis)

    • time_limited() can now indicate whether its iterator has expired (thanks to roysmith)

    • The implementation of unique_everseen() was improved (thanks to plammens)

  • Other changes:
    • Various documentation updates (thanks to cthoyt, Evantm, and cyphase)


  • New itertools
  • Changes to existing itertools
    • chunked() and sliced() now accept a strict parameter (thanks to shlomif and jtwool)

  • Other changes
    • Python 3.5 has reached its end of life and is no longer supported.

    • Python 3.9 is officially supported.

    • Various documentation fixes (thanks to timgates42)


  • New itertools
  • Changes to existing itertools:
    • The is_sorted() implementation was improved (thanks to cool-RR)

    • The groupby_transform() now accepts a reducefunc parameter.

    • The last() implementation was improved (thanks to brianmaissy)

  • Other changes
    • Various documentation fixes (thanks to craigrosie, samuelstjean, PiCT0)

    • The tests for distinct_combinations() were improved (thanks to Minabsapi)

    • Automated tests now run on GitHub Actions. All commits now check:
      • That unit tests pass

      • That the examples in docstrings work

      • That test coverage remains high (using coverage)

      • For linting errors (using flake8)

      • For consistent style (using black)

      • That the type stubs work (using mypy)

      • That the docs build correctly (using sphinx)

      • That packages build correctly (using twine)



  • New itertools
  • Changes to existing itertools:
  • Other changes
    • Type stubs are now tested with stubtest (thanks to ilai-deutel)

    • Tests now run with python -m unittest instead of python test (thanks to jdufresne)


  • Bug fixes
    • The .pyi files for typing were updated. (thanks to blueyed and ilai-deutel)

  • Changes to existing itertools:
    • numeric_range() now behaves more like the built-in range(). (thanks to jferard)

    • bucket() now allows for enumerating keys. (thanks to alexchandel)

    • sliced() now should now work for numpy arrays. (thanks to sswingle)

    • seekable() now has a maxlen parameter.


  • Bug fixes
    • partition() works with pred=None again. (thanks to MSeifert04)

  • New itertools
  • Changes to existing itertools:
    • The implementation for divide() was improved. (thanks to jferard)


  • Bug fixes
    • The type stub files are now part of the wheel distribution (thanks to keisheiled)


  • Bug fixes
    • The type stub files now work for functions imported from the root package (thanks to keisheiled)


  • New itertools and other additions
    • This library now ships type hints for use with mypy. (thanks to ilai-deutel for the implementation, and to gabbard and fmagin for assistance)

    • split_when() (thanks to jferard)

    • repeat_last() (thanks to d-ryzhikov)

  • Changes to existing itertools:
  • Other changes
    • Python 3.4 has reached its end of life and is no longer supported.

    • Python 3.8 is officially supported. (thanks to jdufresne)

    • The collate function has been deprecated. It raises a DeprecationWarning if used, and will be removed in a future release.

    • one() and only() now provide more informative error messages. (thanks to gabbard)

    • Unit tests were moved outside of the main package (thanks to jdufresne)

    • Various documentation fixes (thanks to kriomant, gabbard, jdufresne)



  • New itertools
  • Changes to existing itertools:
    • numeric_range() now supports ranges specified by datetime.datetime and datetime.timedelta objects (thanks to MSeifert04 for tests).

    • difference() now supports an initial keyword argument.

  • Other changes
    • Various documentation fixes (thanks raimon49, pylang)


The major version update is due to the change in the default behavior of collapse(). It now treats bytes objects the same as str objects. This aligns its behavior with always_iterable().

>>> from more_itertools import collapse
>>> iterable = [[1, 2], b'345', [6]]
>>> print(list(collapse(iterable)))
[1, 2, b'345', 6]


  • Major changes:
    • Python 2.7 is no longer supported. The 5.0.0 release will be the last version targeting Python 2.7.

    • All future releases will target the active versions of Python 3. As of 2019, those are Python 3.4 and above.

    • The six library is no longer a dependency.

    • The accumulate() function is no longer part of this library. You may import a better version from the standard itertools module.

  • Changes to existing itertools:
    • The order of the parameters in grouper() have changed to match the latest recipe in the itertools documentation. Use of the old order will be supported in this release, but emit a DeprecationWarning. The legacy behavior will be dropped in a future release. (thanks to jaraco)

    • distinct_permutations() was improved (thanks to jferard - see also permutations with unique values at StackOverflow.)

    • An unused parameter was removed from substrings(). (thanks to pylang)

  • Other changes:
    • The docs for unique_everseen() were improved. (thanks to jferard and MSeifert04)

    • Several Python 2-isms were removed. (thanks to jaraco, MSeifert04, and hugovk)


  • New itertools:
  • Changes to existing itertools:
    • ilen() was optimized a bit (thanks to MSeifert04, achampion, and bmintz)

    • first_true() now returns None by default. This is the reason for the major version bump - see below. (thanks to sk and OJFord)

  • Other changes:
    • Some code for old Python versions was removed (thanks to hugovk)

    • Some documentation mistakes were corrected (thanks to belm0 and hugovk)

    • Tests now run properly on 32-bit versions of Python (thanks to Millak)

    • Newer versions of CPython and PyPy are now tested against

The major version update is due to the change in the default return value of first_true(). It’s now None.

>>> from more_itertools import first_true
>>> iterable = [0, '', False, [], ()]  # All these are False
>>> answer = first_true(iterable)
>>> print(answer)


  • New itertools:
  • 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



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


  • New itertools:
  • 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:
  • 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.