key names for picks

gistfile1.py

class Pick(db.Model):
    # Models a user's prediction of which team will win a game.
    user = db.ReferenceProperty(User)
    game = db.ReferenceProperty(Game)
    picked_team = db.ReferenceProperty(Team)

    @classmethod
    def make_key_name(cls, user, game):
        user_key = str(user.key())
        game_key = str(game.key())
        return "%s_%s" % (user_key, game_key)

    def __init__(self, *args, **kwargs):
        # A trick to inject a key_name into the default constructor.
        if not kwargs.has_key('key') and not kwargs.has_key('key_name'):
            key_name = self.__class__.make_key_name(kwargs['user'], kwargs['game'])
            kwargs['key_name'] = key_name
        db.Model.__init__(self, *args, **kwargs)