Question

I want a nice convenient attribute to do the following:

from django.contrib.auth.models import User
user = User.objects.get(id=2)
user.company
<Company: Big Company L.L.C>

I am currently solving this using lambda. In searching for an answer it looks like perhaps the “right” way to solve this would be to use types.MethodType but I can’t seem to get my head around it. Yes, I have read Raymond excellent guide but I’m clearly missing something.. Here is my current solution for those who are interested..

# Defined Elsewhere
class User:
    name = models.CharField(max_length=32)
class Company(models.Model):
    users =  models.ManyToManyField(User, related_name="companies", blank=True, null=True)

# Here is the meat of this..
class UserProfile(models.Model):
    """This defines Users"""
    user = models.OneToOneField(User)

    def get_company(self):
        try:
            companies = self.user.companies.all()[0]
        except (AttributeError, IndexError):
            return None

User.company = property(lambda u: UserProfile.objects.get_or_create(user=u)[0].get_company())

Right now this works.. But is there a better way – I’m not crazy about lambdas??

Answer 1

I’m not quite sure I understand correctly what your goal is, but from what I think I understand, it doesn’t seem necessary to do any crazy stuff with descriptors here, let alone types.MethodType. A simple property is fine, and if you don’t like the lambda, you can use an ordinary function decorated with @property:

class User:
    name = models.CharField(max_length=32)
    @property
    def company(self):
        return UserProfile.objects.get_or_create(user=self)[0].get_company())

Edit: If you can’t touch the User class, you can create a derived class adding the desired property:

class MyUser(User):
    @property
    def company(self):
        return UserProfile.objects.get_or_create(user=self)[0].get_company())