Iterable chunker with no batch size limits

gistfile1.py

def chunker(iterable=None, chunklen=None):
    """Collects data into fixed-length chunks.

    Returns: iterator of iterators. Does not pad the last chunk.
    Raises: TypeError on bad iterable or chunklen

    Example: chunker("abcde", 2) returns (('a', 'b'), ('c', 'd'), ('e'))

    This is better than the functools 'grouper' recipe (using izip on
    [iter(iterable)] * n) in that there is no performance penalty for
    really large batches.

    """

    # for chunklen=3 generates (0,0,0,1,1,1,0,0,0,1,1,1,...)
    keys = (
        key
        for n in itertools.cycle((0, 1))
        for key in itertools.repeat(n, chunklen)
    )

    # ((a,b,c),(d,e,f),...)
    groups = itertools.groupby(
        iter(iterable),
        key=lambda v: next(keys),
    )

    return (v for _, v in groups)