Check out this video on GCD. I have embedded it below.

Here is the code for gcd.py.

def gcd(a,b):
    if a == 0 and b == 0:
        raise ValueError
    if a < 0:
        a = -a
    if b < 0:
        b = -b
    while b%a > 0:
        b, a = a, b%a
    return a
if __name__ == "__main__":
    print(gcd(7776, 1048576))
    print(gcd(95238908341908231432498324980875, 34904249809812494329625))