Python错误：赋值之前引用的局部变量

Question

这是我的代码：

import time

GLO = time.time()

def Test():
    print GLO
    temp = time.time();
    print temp
    GLO = temp

Test()

Traceback (most recent call last): File "test.py", line 11, in Test() File "test.py", line 6, in Test print GLO UnboundLocalError: local variable 'GLO' referenced before assignment

添加GLO = temp时发生错误，如果我对其进行注释，则函数可以成功执行，为什么？

如何设置GLO = temp？

Answer 1

在测试方法中指定要引用全局声明的GLO变量，如下所示

def Test():
    global GLO #tell python that you are refering to the global variable GLO declared earlier.
    print GLO
    temp = time.time();
    print temp
    GLO = temp

类似的问题可以在这里找到： Using a global variable within a method

Answer 2

Python首先查看整个函数范围。所以你的GLO指的是下面的那个，而不是全局的。并引用LEGB rule。

GLO = time.time()

def Test(glo):
    print glo
    temp = time.time();
    print temp
    return temp

GLO = Test(GLO)

或者

GLO = time.time()

def Test():
    global GLO
    print GLO
    temp = time.time();
    print temp
    GLO =  temp

Test()