gistfile1.py

class Blogger(db.Model):
    class Helper:
        model = None
        @classmethod
        def createDefaultNo(cls):
            bloggers = cls.model.all().fetch(1000)
            if len(bloggers) == 0:
                return 1
            else:
                return max(bloggers, key=lambda x:x.no).no + 1

    no = db.IntegerProperty(required=True, default=Helper.createDefaultNo)
    name = db.StringProperty(required=True)
    date_created = db.DateTimeProperty(auto_now_add=True)

    def __unicode__(self):
        return '%2d - %s' % (self.no, self.name)
Blogger.Helper.model = Blogger