Python Primal Number functions

python_primal_numbers.py

import random, sys

"""
    Miller Rabin Probabilistic Primality Test
"""
def miller_rabin_pass(a, s, d, n):
    a_to_power = pow(a, d, n)
    if a_to_power == 1:
        return True
    for i in xrange(s-1):
        if a_to_power == n - 1:
            return True
        a_to_power = (a_to_power * a_to_power) % n
    return a_to_power == n - 1

def miller_rabin(n):
    # compute s and d
    d = n - 1
    s = 0
    # Using bit shifts to compute d rapidly, and only test its least 
    # significant bit to determine if it is odd
    while d % 2 == 0:
        d >>= 1
        s += 1
    
    # 20 times is enough to make the 1/4^k error rate negligible
    for repeat in xrange(20):
        a = 0
        while a == 0:
            a = random.randrange(n)
        if not miller_rabin_pass(a, s, d, n):
            return False
    return True

def findPrimes(num_set):
    """
        Takes a number set and returns a list of the primes in that set.
        Using set() to remove any duplicates that may be passed in to it.
    """
    return [x for x in set(num_set) if miller_rabin(x)]