Question

Is it possible to set default value of field in data model to id() of the data model?

something like

class MyModel(db.Model):
    myID = db.IntegerProperty(default=self.id())
    desc = db.StringProperty()

Answer 1

You can’t. The default you’re setting there is in a class variable, and will be the same for all instances created after the class definition is read. If self.id() actually made sense in this context (it doesn’t; self is undefined), you’d be getting something like the id of the class, and assigning it as the default to all new instances.

The id isn’t actually assigned to the entity until it is written to the datastore, so you can’t, in principle, know what it is at the time of instantiation. You can set a property to the id after you’ve written the entity, but you almost certainly don’t really want to do this anyway.