More-itertools

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* 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)
* :func:`split_when` (thanks to jferard)
* :func:`repeat_last` (thanks to d-ryzhikov)

* Changes to existing itertools:
* The implementation for :func:`set_partitions` was improved. (thanks to jferard)
* :func:`partition` was optimized for expensive predicates. (thanks to stevecj)
* :func:`unique_everseen` and :func:`groupby_transform` were re-factored. (thanks to SergBobrovsky)
* The implementation for :func:`difference` was improved. (thanks to Jabbey92)

* 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.
* :func:`one` and :func:`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)

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* New itertools
* :func:`distinct_combinations`
* :func:`set_partitions` (thanks to kbarrett)
* :func:`filter_except`
* :func:`map_except`

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* New itertools
* :func:`ichunked` (thanks davebelais and youtux)
* :func:`only` (thanks jaraco)

* Changes to existing itertools:
* :func:`numeric_range` now supports ranges specified by
``datetime.datetime`` and ``datetime.timedelta`` objects (thanks to MSeifert04 for tests).
* :func:`difference` now supports an *initial* keyword argument.


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

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* New itertools:
* :func:`time_limited`
* :func:`partitions` (thanks to rominf and Saluev)
* :func:`substrings_indexes` (thanks to rominf)

* Changes to existing itertools:
* :func:`collapse` now treats ``bytes`` objects the same as ``str`` objects. (thanks to Sweenpet)

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

.. code-block:: python

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

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* 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 :func:`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 :func:`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)
* :func:`distinct_permutations` was improved (thanks to jferard - see also `permutations with unique values <https://stackoverflow.com/questions/6284396/permutations-with-unique-values>`_ at StackOverflow.)
* An unused parameter was removed from :func:`substrings`. (thanks to pylang)

* Other changes:
* The docs for :func:`unique_everseen` were improved. (thanks to jferard and MSeifert04)
* Several Python 2-isms were removed. (thanks to jaraco, MSeifert04, and hugovk)

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* New itertools:
* :func:`split_into` (thanks to rovyko)
* :func:`unzip` (thanks to bmintz)
* :func:`substrings` (thanks to pylang)

* Changes to existing itertools:
* :func:`ilen` was optimized a bit (thanks to MSeifert04, achampion, and bmintz)
* :func:`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
:func:`first_true`. It's now ``None``.

.. code-block:: python

>>> from more_itertools import first_true
>>> iterable = [0, '', False, [], ()] All these are False
>>> answer = first_true(iterable)
>>> print(answer)
None