[Tutor] Strange modulus problem

[Chris Keelan]

I'm working on a bit of code to determine all of the factors up to and 
including a number entered by the user. Here's my code:

#!/usr/bin/python

import string

num=raw_input("Enter a number: ")
num_int=string.atoi(num)

factor_range= range(1, num_int + 1)

for item in factor_range:
    if num_int % item > 0:
        factor_range.remove(item)
        

print 'The factors are %s' % factor_range


But when I run it, I get the following weird output:

>>Enter a number: 6
The factors are [1, 2, 3, 5, 6]


Why doesn't '5' fail the if test and get removed? If I modify the code so 
that it prints the modulus of each item, 5 correctly evalutates to '1'. What 
gives?

- Chris