Karatsuba Algortihm for Integer Multiplication

karatsuba.py

from random import randint

def karatsuba(x, y):
    if (x<10) or (y<10):
        return x*y
    
    x_str = str(x)
    x_n = len(x_str)    
    y_str = str(y)
    y_n = len(y_str)    
    m = max(x_n, y_n)
    m2 = int(m/2)

    a = int(x_str[:-m2])
    b = int(x_str[-m2:])
    c = int(y_str[:-m2])
    d = int(y_str[-m2:])
    
    ac = karatsuba(a,c)
    bd = karatsuba(b,d)
    abcd = karatsuba((a+b),(c+d))
    
    return (10**(2*m2))*ac + (10**m2)*(abcd-ac-bd) + bd

for i in range(10):
    x = randint(1,10000)
    y = randint(1,10000)
    
    expected = x * y
    result = karatsuba(x, y)
    
    print ("%d and %d:" % (x,y))
    print ('expected: ', expected)
    print ('actual:   ', result)
    if result != expected:
        print ("Error with: " + str(x) + " " + str(y))