Don't understand why UnboundLocalError occurs (closure) [duplicate]

问题：

This question already has answers here : 这个问题在这里已经有了答案：

How to change a global variable from within a function? 如何从函数内部更改全局变量？ (8 answers) (8 个回答)

Using global variables in a function (21 answers) 在函数中使用全局变量21 个回答

Closed 4 years ago . 4年前关闭。

What am I doing wrong here?我在这里做错了什么？

counter = 0

def increment():
  counter += 1

increment()

The above code throws an UnboundLocalError .上面的代码抛出一个UnboundLocalError 。

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解决方案：

参考一： https://en.stackoom.com/question/csBf
参考二： https://stackoom.com/question/csBf