Quick implementation of the Karatsuba multiplication algorithm

Karatsuba.py

"""Quick implementation of the Karatsuba multiplication algorithm while doing 
the Stanford Algortihms Design and Analysis Part 1 Course"""
def karatsuba(x,y):
    if x < 10 and y < 10:
        return x*y
    else:
        if x > y:
            divider = pow(10,len(str(x)) / 2)
        else:
            divider = pow(10,len(str(y)) / 2)
    a = x // divider
    b = x % divider
    c = y // divider
    d = y % divider
    ac = karatsuba(a,c)
    bd = karatsuba(b,d)
    e = a+b
    f = c+d
    ef = karatsuba(e,f)        
    return (ac*pow(divider,2) + bd + ((ef-bd-ac)*divider))