aliquot_sum.py

defaliquot_sum(input_num: int) ->int:
"""
 Finds the aliquot sum of an input integer, where the
 aliquot sum of a number n is defined as the sum of all
 natural numbers less than n that divide n evenly. For
 example, the aliquot sum of 15 is 1 + 3 + 5 = 9. This is
 a simple O(n) implementation.
 @param input_num: a positive integer whose aliquot sum is to be found
 @return: the aliquot sum of input_num, if input_num is positive.
 Otherwise, raise a ValueError
 Wikipedia Explanation: https://en.wikipedia.org/wiki/Aliquot_sum

 >>> aliquot_sum(15)
 9
 >>> aliquot_sum(6)
 6
 >>> aliquot_sum(-1)
 Traceback (most recent call last):
 ...
 ValueError: Input must be positive
 >>> aliquot_sum(0)
 Traceback (most recent call last):
 ...
 ValueError: Input must be positive
 >>> aliquot_sum(1.6)
 Traceback (most recent call last):
 ...
 ValueError: Input must be an integer
 >>> aliquot_sum(12)
 16
 >>> aliquot_sum(1)
 0
 >>> aliquot_sum(19)
 1
 """
ifnotisinstance(input_num, int):
raiseValueError("Input must be an integer")
ifinput_num<=0:
raiseValueError("Input must be positive")
returnsum(
divisorfordivisorinrange(1, input_num//2+1) ifinput_num%divisor==0
 )


if__name__=="__main__":
importdoctest

doctest.testmod()