元類(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)

元類在工作中一般很少用到，除非手寫框架

1、__new__創建類時調用

2、__call__創建與初始化類實例時調用