"Jordan Harry" <[EMAIL PROTECTED]> writes: > I'm trying to write a simple program to calculate permutations. I > created a file called "mod.py" and put the following in it: > > def factorial(n): > a = n > b = n > while a>0 and b>1: > n = (n)*(b-1) > b = b-1
A function that does some calculations internally, but has no 'return' statement and thus implicitly returns 'None'. > def perm(n, r): > a = factorial(n) > b = factorial(n-r) These statements bind the 'None' returned by the 'factorial' function to the names 'a' and 'b'. > q = a / b This attempts to use the '/' operator on 'None' with 'None', which raises the exception you saw. (good sigmonster, have a cookie) -- \ "Pinky, are you pondering what I'm pondering?" "I think so, | `\ Brain, but Zero Mostel times anything will still give you Zero | _o__) Mostel." -- _Pinky and The Brain_ | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
