from django.db import models class Poll(models.Model): question = models.CharField(maxlength=200) def __unicode__(self): return u"Q: %s " % self.question class Choice(models.Model): poll = models.ForeignKey(Poll) choice = models.CharField(maxlength=200) def __unicode__(self): return u"Choice: %s in poll %s" % (self.choice, self.poll) __test__ = {'API_TESTS':""" # Regression test for the use of None as a query value. None is interpreted as # an SQL NULL, but only in __exact queries. # Set up some initial polls and choices >>> p1 = Poll(question='Why?') >>> p1.save() >>> c1 = Choice(poll=p1, choice='Because.') >>> c1.save() >>> c2 = Choice(poll=p1, choice='Why Not?') >>> c2.save() # Exact query with value None returns nothing (=NULL in sql) >>> Choice.objects.filter(id__exact=None) [] # Valid query, but fails because foo isn't a keyword >>> Choice.objects.filter(foo__exact=None) Traceback (most recent call last): ... TypeError: Cannot resolve keyword 'foo' into field. Choices are: id, poll, choice # Can't use None on anything other than __exact >>> Choice.objects.filter(id__gt=None) Traceback (most recent call last): ... ValueError: Cannot use None as a query value # Can't use None on anything other than __exact >>> Choice.objects.filter(foo__gt=None) Traceback (most recent call last): ... ValueError: Cannot use None as a query value # Related managers use __exact=None implicitly if the object hasn't been saved. >>> p2 = Poll(question="How?") >>> p2.choice_set.all() [] """}