python - UnboundLocalError:分配前引用的局部变量

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Don't understand why UnboundLocalError occurs [duplicate]
（8个答案）

waitTime=0.5

def is_ava():
    waitTime = waitTime + 0.1
    print waitTime

if __name__ == '__main__':
    is_ava()

为什么，我已经声明了等待时间。
python版本：2.7

最佳答案

要修改全局变量，需要declare it inside the function as a global variable：

waitTime=0.5

def is_ava():
    global waitTime  # <--------
    waitTime = waitTime + 0.1
    print waitTime

if __name__ == '__main__':
    is_ava()