[Python] media di un generatore

[Marco Beri]

Qualche prova in più:

import itertools

def gen(n):
    i = 1
    while i < n:
        yield i
        i += 1

def avg1():
    n, sum_ = 0, 0.0
    for v in gen(100000):
        sum_ += v
        n += 1
    return sum_ / n

def avg2():
    tot = 0.0
    for n, v in enumerate(gen(100000), 1):
        tot += v
    try:
        return tot / n
    except UnboundLocalError:
        return 0 # ???

def avg3():
    x = itertools.izip(*((i, 1) for i in gen(100000)))
    return float(sum(x.next())) / sum(x.next())


def avg4():
    it1, it2 = itertools.tee(gen(100000))
    try:
        return sum(it1) / float(sum(1 for _ in it2))
    except ZeroDivisionError:
        return 0 # ???

if __name__ == '__main__':
    import timeit
    for s in range(1, 5):
        f = "avg%s" % s
        print f, timeit.timeit(f + "()", setup="from __main__ import %s" %
f, number=100)


*avg1 2.8069589138*
*avg2 2.88984298706*
*avg3 6.68095088005*
*avg4 2.85471391678*

Postmettendo che avg1 e avg3 nel caso di sequenza nulla sbagliano.

Ciao.
Marco.
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