Binary search division in Python

bigdiv.py

import sys

def bigmul(a, b):
    """r = a * b
         where
            r = bidmul(a, b)"""
    xs = list(reversed(digits(a)))
    ys = list(reversed(digits(b)))
    zs = [0 for i in xrange(300)]
    for i in xrange(len(ys)):
        t = 0
        for j in xrange(len(xs)):
            zs[i+j] += ys[i] * xs[j] + t
            t = zs[i+j] / 10
            zs[i+j] %= 10
        zs[len(ys)+len(xs)-1] = t
    return int("".join([str(d) for d in reversed(zs)]))

def bigdiv(a, b):
    """r = (a / b, a % b)
         where
           r = bigdiv(a, b)"""
    i = 1L
    while i < a:
        i = bigmul(i, 2)

    l = 1
    while i > 0:
        c = bigmul((l+i), b)
        if c <= a:
            l += i
        i = i / 2

    return (l, a - bigmul(l, b))

def digits(n):
    """Returns a list of n's digits."""
    r = []
    while n > 0:
        r.append(n % 10)
        n /= 10
    r.reverse()
    return r

if __name__ == "__main__":
    print bigdiv(int(sys.argv[1]), int(sys.argv[2]))