本文旨在说明 父类、子类、子类实例的属性继承关系：
代码语言：javascript复制>>> A = type('A', (), {'name':1})
>>> B = type('B',(A,), {'addr':'beijing'}) #B的父类为A
>>> A.__dict__
mappingproxy({'name': 1, '__module__': '__main__', '__dict__': <attribute '__dict__' of 'A' objects>, '__weakref__': <attribute '__weakref__' of 'A' objects>, '__doc__': None})
>>> B.__dict__
mappingproxy({'addr': 'beijing', '__module__': '__main__', '__doc__': None})
>>> b = B()
>>> b.__dict__
{} #__dict__查看每个对象自身的属性，无法暴露继承的属性
>>> dir(b) #dir()可以查看所有有效属性
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'addr', 'name']
>>> b.addr, b.name #以下代码验证了：上游对象更改属性的值，下游皆会继承该值；若下游对象给属性重新赋值了，那么上游再改变属性值时对下游无影响；
('beijing', 1)
>>> A.name = 999
>>> b.name, B.name
(999, 999)
>>> A.name = 0
>>> b.name, B.name
(0, 0)
>>> B.name = 888
>>> A.name, b.name
(0, 888)
>>> A.name = 777
>>> B.name, b.name
(888, 888)
>>> b.name = 666
>>> A.name, B.name, b.name
(777, 888, 666)
>>> B.name = 555
>>> b.name
666
