Python上下文管理

class people():
    def __init__(self,name):
        self.__name=name
    def __enter__(self):
        print('enter')
    def __exit__(self,exc_ty, exc_val, tb):
        print('exit')
    def say(self,s):
        print(s)

me=people("john")

with me:
   me.say('hello') 

enter
hello
exit