python属性get和set order是什么? [英] What is the python attribute get and set order?

问题描述

Python为我们提供了许多关于实例/类属性的可能性，例如:

Python provides us many possibilities on instance/class attribute, for example:

class A(object):
    def __init__(self):
        self.foo = "hello"

a = A()

有许多方法可以访问/更改self.foo的值:

There are many ways to access/change the value of self.foo:

1. 直接访问a.foo
2. 内部字典a.__dict__['foo']
3. 获取并设置a.__get__和a.__set__，当然有两种预定义的方法.
4. getattribute a.__getattribute__
5. __getattr__和__setattr__
6. 也许更多.

1. direct access a.foo
2. inner dict a.__dict__['foo']
3. get and set a.__get__ and a.__set__,of course there two are pre-defined methods.
4. getattribute a.__getattribute__
5. __getattr__ and __setattr__
6. maybe more.

在阅读源代码时，我总是迷失了他们的最终访问顺序是什么?当我使用a.foo时，如何知道将实际调用哪个方法/属性?

While reading source code, I always get lost of what's their ultimate access order? When I use a.foo, how do I know which method/attribute will get called actually?

推荐答案

bar = a.foo ...

1. 调用a.__getattribute__('foo')
2. 默认情况下依次查找a.__dict__['foo']
如果在A上定义，
3. 或调用foo的.__get__().

1. invokes a.__getattribute__('foo')
2. which in turn by default looks up a.__dict__['foo']
3. or invokes foo's .__get__() if defined on A.

然后将返回值分配给bar.

a.foo = bar ...

1. 调用a.__getattribute__('foo')
2. 默认情况下依次查找a.__dict__['foo']
3. 或如果在A上定义，则调用foo的.__set__(bar).

1. invokes a.__getattribute__('foo')
2. which in turn by default looks up a.__dict__['foo']
3. or invokes foo's .__set__(bar) if defined on A.

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