Factor_finder.py

import math, sys

print('''
Factor Finder, by sinister geek 
      A number's factor are two numbers that, when multiplied with each
      other, produce the number. For example, 2x13 = 26, so 2 and 13 are factors of 26. 1x26 =26, are also factors of 26. We say that 26 has four factors: 1,2,13 and 26.
      If a number only has two factors(1 and itself), we call that a prime number. Otherwise, we call it a composite number.
      Can you discover some prime numbers?
      ''')
while True:
    print('Enter a positive whole number to factor(or QUIT):')
    response = input('> ')
    if response.upper() == 'QUIT':
        sys.exit()

    if not (response.isdecimal() and int(response) > 0):
        continue
    number = int(response)
    factors=[]
    for i in range(1,int(math.sqrt(number)) +1):
        if number % i == 0:
            factors.append(i)
            factors.append(number // i)
    factors = list(set(factors))
    factors.sort()
    for i, factor in enumerate(factors):
        factors[i] = str(factor)
    print(', '.join(factors))