测试代码如下：
1classModelMetaClass(type):2def__new__(cls,name,base,attrs):3logging.info("cls is:"+str(cls))4logging.info("name is:"+str(name))5logging.info("base is:"+str(base))6logging.info("attrs is:"+str(attrs))7returntype.__new__(cls,name,base,attrs)8pass9pass1011classModel(dict):12__metaclass__=ModelMetaClass13def__init__(self):14pass15pass1617defmain():18m=Model()1920if__name__=='__main__':21main()
测试结果：
1INFO:root:clsis:<class'__main__.ModelMetaClass'>2INFO:root:nameis:Model3INFO:root:baseis:(<type'dict'>,)4INFO:root:attrsis:{'__module__':'__main__','__metaclass__': <class'__main__.ModelMetaClass'>,'__init__': <function__init__at 0x025C76F0>}
结论就显而易见了。cls是当前类的名字，即类本身。name是通过__metaclass__属性指向ModelMetaClass的类，即要实例化的类，ModelMetaClass拦截了该类的实例化。base是要实例化的类的基类。attrs是要实例化的类的属性集合。