【7.5】自定义元类

元类是什么--元类是创建类的类

#!/user/bin/env python
# -*- coding:utf-8 -*-

# 类也是对象，type创建类的类


def create_class(name):
    if name == 'user':
        class User:
            def __str__(self):
                return 'user'
        return User
    elif name == 'company':
        class Company:
            def __str__(self):
                return 'company'
        return Company


# type动态创建类
User = type('User', (), {})


def say(self):
    return 'i am user'


class BaseClass:
    def answer(self):
        return 'i am baseclass'


# 什么是元类， 元类是创建类的类
class MetaClass(type):
    def __new__(cls, *args, **kwargs):
        return super().__new__(cls, *args, **kwargs)


class User(metaclass=MetaClass):
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return 'user'


# python 中类的实例化过程，会首先寻找metaclass， 通过metaclass去创建user类
# type去创建类对象，实例


if __name__ == '__main__':
    # MyClass = create_class('user')
    # my_obj = MyClass()
    # print(my_obj)
    User = type('User', (BaseClass,), {'name': 'user', 'say': say})
    user = User()
    print(user.name)
    print(user.say())
    print(user.answer())

user
i am user
i am baseclass