How do I define a Python property *outside* of a c

问题:

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

But I get the following error:

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

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

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()

回答1:

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))