[Python-ideas] Batching/grouping function for itertools

[Amber Yust]

After seeing yet another person asking how to do this on #python (and
having needed to do it in the past myself), I'm wondering why itertools
doesn't have a function to break an iterator up into N-sized chunks.

Existing possible solutions include both the "clever" but somewhat
unreadable...

    batched_iter = zip(*[iter(input_iter)]*n)

...and the long-form...

    def batch(input_iter, n):
        input_iter = iter(input_iter)
        while True:
            yield [input_iter.next() for _ in range(n)]

There doesn't seem, however, to be one clear "right" way to do this. Every
time I come up against this task, I go back to itertools expecting one of
the grouping functions there to cover it, but they don't.

It seems like it would be a natural fit for itertools, and it would
simplify things like processing of file formats that use a consistent
number of lines per entry, et cetera.

~Amber
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