python type and __mateclass__和__new__的使用

type:使用type来创建一个类

def func(self):
    print('%s hello world'%self.name)
def __init__(self,name ,age):
    self.name = name
    self.age = age


Foo = type('Foo', (object,), {'test': func,"__init__":__init__})
# type第一个参数：类名
# type第二个参数：当前类的基类
# type第三个参数：类的成员
f =Foo('test',22)
f.test()
print(type(Foo))

__mateclass__和__new__：

class MyType(type):
    def __init__(self,*args,**kwargs):
        print("Mytype __init__",*args,**kwargs)

    def __call__(self, *args, **kwargs):
        print("Mytype __call__", *args, **kwargs)
        obj = self.__new__(self)
        print("obj ",obj,*args, **kwargs)
        print(self)
        self.__init__(obj,*args, **kwargs)
        return obj

    def __new__(cls, *args, **kwargs):
        print("Mytype __new__",*args,**kwargs)
        return type.__new__(cls, *args, **kwargs)

class Foo(object):
    metaclass = MyType#表示被某个对象创建这个类
    def __init__(self,name):
        self.name = name
        print("Foo __init__")

    def __new__(cls, *args, **kwargs):#通过new来实例化__init__.new是用来创建实例的。
        print("Foo __new__",cls, *args, **kwargs)
        return object.__new__(cls)#继承父亲的__new__方法

f = Foo("Alex")
print("f",f)
print("fname",f.name)