Python prime factor calculator

prime_factors.py

from typing import List

def prime_factors(num: int) -> List[int]:
    """
    Searches for numbers that evenly divide the given
    number and makes a list of these numbers, returning
    the list. The product of the list is equivalent to
    the original number as long as it's > 1, returning
    an empty list otherwise.
    """
    
    factors = []
    while 1 < num:
        for factor in range(2 if not factors else factors[-1], num+1):
            if num % factor == 0:
                factors.append(factor)
                num //= factor
                break
    return factors