More-itertools

-----

* 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]

-----

* 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)

-----

* 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

-----

* New itertools:
* :func:`last` (thanks to tmshn)
* :func:`replace` (thanks to pylang)
* :func:`rlocate` (thanks to jferard and pylang)

* Improvements to existing itertools:
* :func:`locate` can now search for multiple items

* Other changes:
* The docs now include a nice table of tools (thanks MSeifert04)

-----

* New itertools:
* :func:`map_reduce` (thanks to pylang)
* :func:`prepend` (from the `Python 3.7 docs <https://docs.python.org/3.7/library/itertools.html#itertools-recipes>`_)

* Improvements to existing itertools:
* :func:`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:
* :func:`split_at` (thanks to michael-celani)
* :func:`circular_shifts` (thanks to hiqua)
* :func:`make_decorator` - see the blog post `Yo, I heard you like decorators <https://sites.google.com/site/bbayles/index/decorator_factory>`_
for a tour (thanks to pylang)
* :func:`always_reversible` (thanks to michael-celani)
* :func:`nth_combination` (from the `Python 3.7 docs <https://docs.python.org/3.7/library/itertools.html#itertools-recipes>`_)

* Improvements to existing itertools:
* :func:`seekable` now has an ``elements`` method to return cached items.
* The performance tradeoffs between :func:`roundrobin` and
:func:`interleave_longest` are now documented (thanks michael-celani,
pylang, and MSeifert04)