factor.py

import itertools
import sys


def erat2():
    D = {}
    yield 2
    for q in itertools.islice(itertools.count(3), 0, None, 2):
        p = D.pop(q, None)
        if p is None:
            D[q * q] = q
            yield q
        else:
            x = p + q
            while x in D or not (x & 1):
                x += p
            D[x] = p


for arg in sys.argv[1:]:
    i = int(arg)
    print(end=f"{i}:")
    for p in erat2():
        if p * p > i:
            break
        while i % p == 0:
            print(end=f" {p}")
            i //= p
    if i > 1:
        print(f" {i}")
    else:
        print()