compute mean in python for a generator

Question

I\'m doing some statistics work, I have a (large) collection of random numbers to compute the mean of, I\'d like to work with generators, because I just need to compute the

Answer 1

Try:

import itertools

def mean(i):
    (i1, i2) = itertools.tee(i, 2)
    return sum(i1) / sum(1 for _ in i2)

print mean([1,2,3,4,5])

tee will duplicate your iterator for any iterable i (e.g. a generator, a list, etc.), allowing you to use one duplicate for summing and the other for counting.

(Note that 'tee' will still use intermediate storage).