UnboundLocalError：分配之前引用的局部变量

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，我已经声明了waitTime。

Python版本：2.7

Answer 1

要修改全局变量，你需要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()