Python 3内置类型之间有什么关系？

Question

In python 3 everything is a object. I drew a diagram about relation of classes. Is this diagram correct?

the hard part is about type and object classes. how are they in relation ? type is a object ? or object is a type ?

>>> x=type
>>> type(x)
<class 'type'>
>>> x=object
>>> type(x)
<class 'type'>

Answer 1

As far as I know, the class relations are kind of like this in Python 3:

• Every class is a subclass of object
• Every class is an instance of type

Every class is created by the type class or an other metaclass, which derives from type . Because of this every class is an instance of type (including type !) Every class will return True for isinstance(cls, type) .

In Python 3, every class is also a subclass from object . Every class or instance will return True for isinstance(cls_or_instance, object)

A special case is metaclasses. A metaclass derives from type , so every metaclass will return True for issubclass(metaclass, type) and isinstance(metaclass, type)

Answer 2

The type object is itself an object. Note though that the inheritance model of python is not the same as in other OO-languges, much of it depends on duck typing rather than inheritance.

Note that type(x) returns the type of the object, that type(object) returns <class 'type'> means nothing more than the type of object (which is the type all objects has) is a type (the type all types are), type itself is a type so the type of it is again type .