Get all prime factors of a number

PrimeFactors.py

# Function to find prime factors of a number
def primeFactors(num):

    # Function to reduce num by a factor
    def reduceByFactor(factor):
        nonlocal num
        while num % factor == 0:
            num = num // factor
        return

    # Init
    primes = set()

    # Reduce by factor of 2
    div = 2
    if num % div == 0:
        primes.add(div)
        reduceByFactor(div)

    # Reduce by all other prime nums    
    div = 3
    while div <= num:
        if num % div == 0:
            primes.add(div)
            reduceByFactor(div)
        div += 2

    return primes