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What is the best way to get all the divisors of a number?

The most part of this code was written by an other programmer, but I cant run his code. Please show me where the mistake is. I was searching a long time. I get the error 'NoneType' object is not iterable (in divisorGen(n)).

from __future__ import division

#calculate the divisors
#this is fast-working-code from:
#http://stackoverflow.com/questions/171765/what-is-the-best-way-to-get-all-the-divisors-of-a-number

def factorGenerator(n):
    for x in range(1,n):
        n = n * 1.0
        r = n / x
        if r % 1 == 0:
            yield x # edited

def divisorGen(n):
    factors = list(factorGenerator(n))
    nfactors = len(factors)
    f = [0] * nfactors
    while True:
        yield reduce(lambda x, y: x*y, [factors[x][0]**f[x] for x in range(nfactors)], 1)
        i = 0
        while True:
            f[i] += 1
            if f[i] <= factors[i][1]:
                break
            f[i] = 0
            i += 1
            if i >= nfactors:
                return

for n in range(100):
    for i in divisorGen(n):
        print i