def chunks(l, n):
    """Yield successive n-sized chunks from l."""
    for i in range(0, len(l), n):
        yield l[i:i + n]

def range_generator(upper, batch_size):
    """Yield successive n-sized chunks from l."""
    return [
        (i, i + batch_size)
        for i in range(0, upper, batch_size)
    ]