python - python导入全局变量的两种方式

Question

我遇到了一个我不明白的情况。我有三个文件:

one.py(可运行):

import two
import three

three.init()
two.show()

二.py:

import three

def show():
    print(three.test)

三.py:

test = 0

def init():
    global test
    test = 1

如我所料，结果是 1。现在让我们修改two.py:

from three import test

def show():
    print(test)

结果是 0。为什么？

Answer 1

一切都与范围有关。 如果您按如下方式更改 one.py，您会看得更清楚。

import three
from three import test

three.init()

print(test)
print(three.test)

它将打印:

0        <== test was imported before init()
1        <== three.test fetches the current value

当您只导入变量时，它会创建一个局部变量，它是一个不可变的整数。

但是如果你像下面这样改变导入语句的顺序，你会得到不同的结果:

import three

three.init()
print(three.test)

from three import test
print(test)

它将打印:

1        <== three.test fetches the current value
1        <== test was imported after init()