python flatten

flatten.py

def make_flatten(fl_types=None):
    if fl_types is None:
        fl_types = (list, tuple)

    def flatten(x):
        for i in x:
            if isinstance(i, fl_types):
                for a in flatten(i):
                    yield a
            else:
                yield i
    return flatten

flatten = make_flatten()

if __name__ == '__main__':
    m = [[[1, 13], [2, 14], [3, 15]],
 [[4, 16], [5, 17], [6]],
 [[7], [8], [9]],
 [[10], [11], [12]]]

    assert list(flatten(m)) == [1, 13, 2, 14, 3, 15, 4, 16, 5, 17, 6, 7, 8, 9, 10, 11, 12]