Python 3 Map 函数不是调用函数 [英] Python 3 Map function is not Calling up function

问题描述

为什么下面的代码不打印任何东西:

Why doesn't following code print anything:

#!/usr/bin/python3
class test:
    def do_someting(self,value):
        print(value)
        return value

    def fun1(self):
        map(self.do_someting,range(10))

if __name__=="__main__":
    t = test()
    t.fun1()

我正在 Python 3 中执行上述代码.我想我遗漏了一些非常基本但无法弄清楚的东西.

I'm executing the above code in Python 3. I think i'm missing something very basic but not able to figure it out.

推荐答案

map() 返回一个迭代器，并且在您要求之前不会处理元素.

map() returns an iterator, and will not process elements until you ask it to.

把它变成一个列表，强制处理所有元素:

Turn it into a list to force all elements to be processed:

list(map(self.do_someting,range(10)))

或使用 collections.deque() 并将长度设置为 0 以在不需要地图输出时不生成列表:

or use collections.deque() with the length set to 0 to not produce a list if you don't need the map output:

from collections import deque

deque(map(self.do_someting, range(10)))

但请注意，对于您的代码的任何未来维护者来说，简单地使用 for 循环会更具可读性:

but note that simply using a for loop is far more readable for any future maintainers of your code:

for i in range(10):
    self.do_someting(i)

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