Из http://docs.python.org/library/itertools.html :
from itertools import izip_longest def grouper(n, iterable, fillvalue=None): "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx" args = [iter(iterable)] * n return izip_longest(fillvalue=fillvalue, *args) i = grouper(3,range(100)) i.next() (0, 1, 2)