def loop_zip(strA, strB):
    """(str, str) => zip()
    Return a zip object containing each letters of strA, paired with letters of strB.
    If strA is longer than strB, then its letters will be paired recursively.
    Example:
        >>> list(loop_zip('ABCDEF', '123'))
        [('A', '1'), ('B', '2'), ('C', '3'), ('D', '1'), ('E', '2'), ('F', '3')]
    """
    assert len(strA) >= len(strB)
    s = ""
    n = 0
    for l in strA:
        try:
            s += strB[n]
        except IndexError:
            n = 0
            s += strB[n]
        n += 1
    return zip(list(strA), list(s))