python高级之元类的用法总结

class A(object):

    def __init__(self, name):
        self.name = name

    def __new__(cls, *args, **kwargs):
        data = object.__new__(cls)
        return data

class A(object):
    v1 = 123

    def func(self):
        return 666


print(A)			#<class '__main__.A'>

A1 = type('A', (object,), {"v1": 123, "func": lambda self: 666})
print(A1)        #<class '__main__.A'>

# 根据类创建对象
obj1 = A1()			#<__main__.A object at 0x0000017049D035E0>
print(obj1)


# 调用对象中的func方法 
print(obj1.func())  #666

class MyType(type):
    pass

# Foo类由MyType创建
class Foo(object, metaclass=MyType):
    pass

class MyType(type):

    def __init__(self, *args, **kwargs):
        print('init')
        super().__init__(*args, **kwargs)

    def __new__(cls, *args, **kwargs):
        # 创建类
        print('new')
        new_cls = super().__new__(cls, *args, **kwargs)
        print(new_cls)
        return new_cls

# 假设Foo是一个对象，由MyType类创建。
class Foo(object, metaclass=MyType):
    pass

class F1(object):
    def __init__(self):
        print('init')

    # def __new__(cls, *args, **kwargs):
    #     print('new')

    def __call__(self, *args, **kwargs):
        print(111)

# 类加括号得到的是对象，执行的是__init__和__new__方法
obj = F1()

# 对象加括号执行call方法
obj()

class MyType(type):

    def __init__(self, *args, **kwargs):
        print('init')
        super().__init__(*args, **kwargs)

    def __new__(cls, *args, **kwargs):
        # 创建类
        print('new')
        new_cls = super().__new__(cls, *args, **kwargs)
        print(new_cls)
        return new_cls

    def __call__(self, *args, **kwargs):
        # 1、调用自己哪个类的__new__方法创建对象
        empty_object=self.__new__(self)
        #2、调用你自己那个类 __init__方法去初始化
        self.__init__(empty_object,*args,**kwargs)

        return empty_object

# 假设Foo是一个对象，由MyType创建。
#  Foo类其实是MyType的一个对象。
# Foo()  ——》MyType对象()
class Foo(object, metaclass=MyType):

    def __init__(self,name):
        self.name=name

v1=Foo('666')

print(v1)
print(v1.name)