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

And then there's always the documentation.

def pairwise(iterable):
    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
    a, b = tee(iterable)
    try:
        b.next()
    except StopIteration:
        pass
    return izip(a, b)

def grouper(n, iterable, padvalue=None):
    "grouper(3, 'abcdefg', 'x') --> ('a','b','c'), ('d','e','f'), ('g','x','x')"
    return izip(*[chain(iterable, repeat(padvalue, n-1))]*n)

Note: these produce tuples instead of substrings, when given a string sequence as input.