models.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import models

from django.db import models
import computed_property


class MyModel(models.Model):
    doubled = computed_property.ComputedIntegerField(compute_from='double_it')
    base = models.IntegerField()
    count = computed_property.ComputedIntegerField('count_related')
 
    def double_it(self):
        return self.base * 2

    @property
    def count_related(self):
        print 'counting!'
        return AnotherModel.objects.filter(related=self).count()

    def as_dict(self):
        return {
            'id': self.id,
            'doubled': self.doubled,
            'count': self.count,
            'base': self.base
        }


class AnotherModel(models.Model):
    related = models.ForeignKey('MyModel', null=True)