Python - TypeError - TypeError: '<' not supported between instances of 'NoneType' and 'int'

Question

TypeError: '<' not supported between instances of 'NoneType' and 'int'

I have looked for an answer in Stack Overflow and found that I should be taking an int(input(prompt)), but that's what I am doing

def main():           while True:             vPopSize = validinput("Population Size: ")             if vPopSize < 4:                 print("Value too small, should be > 3")                 continue             else:                 break  def validinput(prompt):     while True:         try:             vPopSize = int(input(prompt))         except ValueError:             print("Invalid Entry - try again")             continue         else:             break 

Answer 1

This problem also comes up when migrating to Python 3.

In Python 2 comparing an integer to None will "work," such that None is considered less than any integer, even negative ones:

>>> None > 1 False >>> None < 1 True 

In Python 3 such comparisons raise a TypeError:

>>> None > 1 Traceback (most recent call last):   File "<stdin>", line 1, in <module> TypeError: '>' not supported between instances of 'NoneType' and 'int'  >>> None < 1 Traceback (most recent call last):   File "<stdin>", line 1, in <module> TypeError: '<' not supported between instances of 'NoneType' and 'int'