factors.py

View source code here on GitHub!

Includes

• prime_factors()

• functools.reduce()

• itertools.combinations()

• operator.mul()

python.src.lib.factors.proper_divisors(num: int) → Iterator[int]

from functools import reduce
from itertools import combinations
from operator import mul
from typing import Iterator, Set

from .primes import prime_factors


def proper_divisors(num: int) -> Iterator[int]:
    factors = tuple(prime_factors(num))
    seen: Set[int] = set()
    yield 1
    for x in range(1, len(factors)):
        for combo in combinations(factors, x):
            ret = reduce(mul, combo, 1)
            if ret not in seen:
                yield ret
                seen.add(ret)
        seen.clear()

Tags: python-iterator, divisor-count, divisibility