[py]数据描述符优先级

实例查找属性的顺序:

类属性 > 数据描述符 > 实例属性 > 非数据描述符 > __getattr__

类属性>数据描述符>实例属性

class Str:
    def __get__(self, instance, owner):
        print("执行: __get__")

    def __set__(self, instance, value):
        print("执行: __set__")

    def __delete__(self, instance):
        print("执行: __delete__")

class A:
    name = Str()

    def __init__(self):
        self.name = "mm"

a = A()
A.name = "maotai_class"  # 添加类属性

print(a.name) # 1.优先打印类属性 2.其次打印数据描述符 3.最后打印实例属性

实例属性>非数据描述符

class Str:
    def __get__(self, instance, owner):
        print("执行: __get__")

    # def __set__(self, instance, value):
    #     print("执行: __set__")

    # def __delete__(self, instance):
    #     print("执行: __delete__")

class A:
    name = Str()

a = A()
a.name = "maotai"
print(a.__dict__)

--
{'name': 'maotai'}

class Str:
    def __get__(self, instance, owner):
        print("执行: __get__")

    def __set__(self, instance, value):
        print("执行: __set__")

    # def __delete__(self, instance):
    #     print("执行: __delete__")

class A:
    name = Str()

a = A()
a.name = "maotai"
print(a.__dict__)

--
执行: __set__
{}

非数据描述符>找不到

class A:
    def __getattr__(self, item):
        print("触发__getattr__")

a = A()
a.xxx # 触发__getattr__