10001st prime. http://projecteuler.net/problem=7

10001st_prime.py

#-*- coding: utf8 -*-

def isPrime(num, ps):
    for i in ps:
        if num%i == 0:
            return False
        if i**2 > num:
            break
    return True

def primes(total=10001):
    ps = [2,3,5,7,11,13]
    while total - len(ps) > 0:
        tmp = ps[-1]+2
        while True:
            if isPrime(tmp, ps):
                ps.append(tmp)
                break
            else:
                tmp += 2
    return ps[-1]


print primes(10001)

Very fast!