如何定义类定义的 Python 属性 *outside*? [英] How do I define a Python property *outside* of a class definition?

问题描述

我想在类定义的外部定义一个 Python 属性:

I would like to define a Python property outside of a class definition:

c = C()
c.user = property(lambda self: User.objects.get(self.user_id))
print c.user.email

但我收到以下错误:

AttributeError: 'property' object has no attribute 'email'

在类定义之外定义属性的正确语法是什么?

What is the correct syntax for defining a property outside of a class definition?

顺便说一句:我正在使用 生菜

Btw: I'm using lettuce

from lettuce import *
from django.test.client import Client
Client.user_id = property(lambda self: self.browser.session.get('_auth_user_id'))
Client.user = property(lambda self: User.objects.get(self.user_id))

@before.each_scenario 
def set_browser(scenario):
    world.browser = Client()

推荐答案

像 c 这样的对象实例不能有属性；只有像 C 这样的类可以有属性.所以需要在类上设置属性，而不是实例，因为Python只在类上查找:

Object instances like c cannot have properties; only classes like C can have properties. So you need to set the property on the class, not the instance, because Python only looks for it on the class:

C.user = property(lambda self: User.objects.get(self.user_id))

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