title: Query distinct list of choices for Django form with App Engine Datastore
body: <p>I've been trying to figure this out for hours across a couple of days, and can not get it to work. I've been everywhere. I'll continue trying to figure it out, but was hoping for a quicker solution. I'm using App Engine datastore + Django.</p>
  
  <p>Using a query in a view and custom forms, I was able to get a list to the form but then I was not able to post. I have been trying to figure out how to dynamically add the choices as part of the Django form... I've tried various ways with no success. Help!</p>
  
  <p>Below are the two models. I'd like to get a distinct list of address_id to show in the location field in InfoForm. This fields could (and maybe should) be named the same, but I thought it'd be easier if they were named different.</p>
  
  <pre><code>class Info(db.Model):
      user = db.UserProperty()
      location = db.StringProperty()
      info = db.StringProperty()
      created = db.DateTimeProperty(auto_now_add=True)
      modified = db.DateTimeProperty(auto_now=True)
  
  class Locations(db.Model):
      user = db.UserProperty()
      address_id = db.StringProperty()
      address = db.StringProperty()
  
  class InfoForm(djangoforms.ModelForm):
      info = forms.ChoiceField(choices=INFO_CHOICES)
      location = forms.ChoiceField()
      class Meta:
              model = Info
              exclude = ['user','created','modified']
  </code></pre>