def monomial_gcd(a, b):
    """Greatest common divisor of tuples representing monomials.

       Lets compute GCD of x**3*y**4*z and x*y**2:

       >>> monomial_gcd((3, 4, 1), (1, 2, 0))
       (1, 2, 0)

       which gives x*y**2.

    """
    return tuple([ min(x, y) for x, y in zip(a, b) ])