recipes for groupers from http://docs.python.org/library/itertools.html#recipes

groupers.py

def grouperchunker(seq, size):
    return (seq[pos:pos + size] for pos in xrange(0, len(seq), size))

for group in grouper(animals, 3):
    print group


from itertools import 

def grouper(n, iterable, fillvalue=None):
    "Collect data into fixed-length chunks or blocks"
    # grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx
    args = [iter(iterable)] * n
    return izip_longest(fillvalue=fillvalue, *args)