python generator太慢了，无法使用它.我为什么要使用它?什么时候? [英] python generator is too slow to use it. why should I use it? and when?

问题描述

最近我遇到一个问题，即在 iterator ， list comprehension ， iter(list comprehension)和中，哪一个是最快的东西>发电机.然后制作简单的代码，如下所示.

Recently I got question about which one is the most fastest thing among iterator, list comprehension, iter(list comprehension) and generator. and then make simple code as below.

n = 1000000
iter_a = iter(range(n))
list_comp_a = [i for i in range(n)]
iter_list_comp_a = iter([i for i in range(n)])
gene_a = (i for i in range(n))

import time
import numpy as np

for xs in [iter_a, list_comp_a, iter_list_comp_a, gene_a]:
    start = time.time()
    np.sum(xs)
    end = time.time()
    print((end-start)*100)

结果如下.

0.04439353942871094 # iterator
9.257078170776367 # list_comprehension
0.006318092346191406 # iterator of list_comprehension
7.491207122802734 # generator 

发电机比其他东西要慢.我不知道什么时候有用?

generator is so slower than other thing. and I don't know when it is useful?

推荐答案

生成器不会一次将所有元素存储在内存中.它们一次 yield 一次，这种行为使它们的存储效率更高.因此，当内存受到限制时，您可以使用它们.

generators do not store all elements in a memory in one go. They yield one at a time, and this behavior makes them memory efficient. Thus you can use them when memory is a constraint.

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