UnboundLocalError：赋值前引用的局部变量

Question

waitTime=0.5

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

if __name__ == '__main__':
    is_ava()

为什么UnboundLocalError: local variable 'waitTime' referenced before assignment，我已经宣布了waitTime。

Python版本：2.7

Answer 1

要修改全局变量，您需要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()