带有导入的全局变量 [英] Global variable with imports

问题描述

myGlobal = "hello"

def changeGlobal():
   myGlobal="bye"

second.py

from first import *

changeGlobal()
print myGlobal

我得到的输出是

你好

尽管我认为应该是

再见

为什么在调用changeGlobal()函数后全局变量myGlobal没有更改?

Why doesn't the global variable myGlobal changes after the call to the changeGlobal() function?

推荐答案

尝试:

def changeGlobal():
    global myGlobal
    myGlobal = "bye"

实际上，这也不起作用. import *时，您将创建一个新的 local 模块全局myGlobal，该模块不受您想要的更改的影响(只要不对变量进行突变，请参见下文).您可以改用以下方法:

Actually, that doesn't work either. When you import *, you create a new local module global myGlobal that is immune to the change you intend (as long as you're not mutating the variable, see below). You can use this instead:

import nice

nice.changeGlobal()
print nice.myGlobal

或者:

myGlobal = "hello"

def changeGlobal():
   global myGlobal
   myGlobal="bye"

changeGlobal()

但是，如果您的全局变量是可变容器，那么您现在持有对可变变量的引用，并且能够看到对其所做的更改:

However, if your global is a mutable container, you're now holding a reference to a mutable and are able to see changes done to it:

myGlobal = ["hello"]

def changeGlobal():
    myGlobal[0] = "bye"

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