Simon Willison’s Weblog

The Google App Engine model class, db.Model, is not the same as the model class used by Django. As a result, you cannot directly use the Django forms framework with Google App Engine. However, Google App Engine includes a module, db.djangoforms, which casts between the datastore models used with Google App Engine and the Django models specification. In most cases, you can use db.djangoforms.ModelForm in the same manner as the Django framework.

— Google App Engine docs