Splitting a list into even chunks.

  • split
  • chunk
  • list

Using the grouper recipe from the itertools documentation:

>>> from itertools import zip_longest # Use izip_longest for Python 2.x
>>> def grouper(iterable, n, fillvalue=None):
        args = [iter(iterable)] * n
        return zip_longest(*args, fillvalue=fillvalue)
>>> list(grouper(a, 3))
[(1, 2, 3), (4, 5, 6), (7, None, None)]

Another approach to exclude worrying about fill values (although it’s slightly less efficient) is to build a list of the certain chunk size and yield, eg:

from itertools import islice

def grouper(iterable, n):
    yield from iter(lambda it=iter(iterable): list(islice(it, n)), [])
    # Or in Python 2.7, where `yield from` doesn't exist yet, use:
    # for chunk in iter(lambda it=iter(iterable): list(islice(it, n)), []):
    #     yield chunk