batch.py

from __future__ import print_function, unicode_literals

from six import itertools


def batch(iterable, size):
    """ Generates slices of items in groups of `size` length.
    >>> for group in batch(range(10), size=4):
            print(group)
    (0, 1, 2, 3)
    (4, 5, 6, 7)
    (8, 9)
    """
    sentinel = object()
    items = itertools.repeat(iter(iterable), size)

    for group in itertools.izip_longest(*items, fillvalue=sentinel):
        yield tuple(
            item for item in group if item is not sentinel
        )

This is based off of implementations I found:

• https://stackoverflow.com/a/8998040/28360
• https://stackoverflow.com/a/38087899/28360
• http://pastebin.com/YkKFvm8b
• https://git.io/vbN4c

If the size of each chunk is set very high, this should be altered to yield a generator instead of a tuple. But this isn't necessary if size < 10 ** 6.