元类(一)

# -*- coding: utf-8 -*-
""" 
@Time    : 2023-06-25 23:14
@Description :
@Author  : Mr.Gu
"""
import time
import types


class Meta(type):
    def __new__(cls, name, bases, attrs):
        for key, value in attrs.items():
            if isinstance(value, types.FunctionType) and not key.startswith("_"):
                attrs[key] = property(value)
        return super().__new__(cls, name, bases, attrs)

    def __call__(cls, *args, **kwargs):
        inst = super().__call__(*args, **kwargs)
        inst.created_at = time.time()
        return inst


class Valley(metaclass=Meta):
    def func(self):
        print("testing")


Valley().func
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