class Go:
     def __init__(self):
         self.dict={}
         print("开始")
     def __del__(self):
         print("结束")
     def __getitem__(self,value):
         if type(value)==str:
             return 123
         else:
             print(value.start)
             print(value.stop)
             print(value.step)
             return "state"
         return self.dict[value]
     def __setitem__(self,key,value):
         self.dict[key]=value
1
 3

 None

 结束