python中类型与对象的实例关系？

Question

显示class类型和对象之间的关系：

issubclass(type,object)
True
issubclass(object,type)
False

很明显type派生自object,object是type的父亲class,type是儿子class 个 object。

isinstance(type,object)
True
isinstance(object,type)
True

如何理解type是object的实例，反之亦然？

Answer 1

有用的定义

isinstance(object, classinfo)

Return True if the object argument is an instance of the classinfo argument, or of a (direct, indirect or virtual) subclass thereof.
https://docs.python.org/3.9/library/functions.html?highlight=isinstance#isinstance

1) type 是 object

的实例

• 所有数据都由对象表示，object 是所有 类
的基础

Objects are Python’s abstraction for data. All data in a Python program is represented by objects or by relations between objects.
https://docs.python.org/3.9/reference/datamodel.html#types

object is a base for all classes.
https://docs.python.org/3.9/library/functions.html?highlight=object#object

• type 继承自 object (https://docs.python.org/3.9/library/functions.html?highlight=object#type) 所以 type 既是子类又是 object 的实例，使用 isinstance 描述。

2) object 是 type

的实例

• object 是类型对象。换句话说，object 是类型，type

Type Objects
Type objects represent the various object types. An object’s type is accessed by the built-in function type()
https://docs.python.org/3.9/library/stdtypes.html?highlight=subclass#type-objects

• type(object) # returns type

• type(type) # returns type

• object.__class__ # returns type

• type.__class__ # returns type

• 这有助于我们理解 isInstance(object, type) 将如何 return True.

• 一种直观的思考方式是 object 对象的类型是 type 但 object不是 type 的子类，因为它不继承自 type