django/tests/modeltests/lookup/models.py

"""
7. The lookup API

This demonstrates features of the database API.
"""

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)
    class Meta:
        ordering = ('name', )

class Article(models.Model):
    headline = models.CharField(max_length=100)
    pub_date = models.DateTimeField()
    author = models.ForeignKey(Author, blank=True, null=True)
    class Meta:
        ordering = ('-pub_date', 'headline')

    def __unicode__(self):
        return self.headline

class Tag(models.Model):
    articles = models.ManyToManyField(Article)
    name = models.CharField(max_length=100)
    class Meta:
        ordering = ('name', )