factor.py

cesarkawakami@pandambp13r:~/temp/TheBigDeal [crap3]
$ cat factor.py
import collections
import math


def factor(n):
    factors = collections.defaultdict(int)
    for candidate in range(2, int(math.sqrt(n))):
        if n == 1:
            break
        while n % candidate == 0:
            n /= candidate
            factors[candidate] += 1

    assert n == 1
    return factors


if __name__ == "__main__":
    print(factor(600851475143))

cesarkawakami@pandambp13r:~/temp/TheBigDeal [crap3]
$ time python3 factor.py
defaultdict(<class 'int'>, {6857: 1, 839: 1, 1471: 1, 71: 1})

real	0m0.026s
user	0m0.020s
sys	0m0.005s