Iterate over a python sequence in multiples of n?

Question

How do I process the elements of a sequence in batches, idiomatically?

For example, with the sequence \"abcdef\" and a batch size of 2, I would like to do something

Answer 1

The itertools doc has a recipe for this:

from itertools import izip_longest

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

Usage:

>>> l = [1,2,3,4,5,6,7,8,9]
>>> [z for z in grouper(l, 3)]
[(1, 2, 3), (4, 5, 6), (7, 8, 9)]