元类(一)
1 # -*- coding: utf-8 -*- 2 """ 3 @Time : 2023-06-25 23:14 4 @Description : 5 @Author : Mr.Gu 6 """ 7 import time 8 import types 9 10 11 class Meta(type): 12 def __new__(cls, name, bases, attrs): 13 for key, value in attrs.items(): 14 if isinstance(value, types.FunctionType) and not key.startswith("_"): 15 attrs[key] = property(value) 16 return super().__new__(cls, name, bases, attrs) 17 18 def __call__(cls, *args, **kwargs): 19 inst = super().__call__(*args, **kwargs) 20 inst.created_at = time.time() 21 return inst 22 23 24 class Valley(metaclass=Meta): 25 def func(self): 26 print("testing") 27 28 29 Valley().func 30 print(Valley().created_at)
元类在工作中一般很少用到,除非手写框架
1、__new__创建类时调用
2、__call__创建与初始化类实例时调用