Question

Hi am going through the docs of GAE and needed a small clarification. If I have my db model something like this:-

class Phone(Model):
  phone_name = db.StringProperty()

r = Phone(Nokia, key_name='first')
r.put()

Now if I have to retrieve this entity but I dont know the key, can I construct the key like this:

k=db.Key('Phone','first')

and once the key is constructed, can the entity be retrieved like this:-

r=db.get(k)

Answer 1

You’re close. The only major difference is that you have to pass the actual class instead of a string representing the class name, and that you have to use the Key.from_path() factory method rather than the default constructor:

class Phone(Model):
  phone_name = db.StringProperty()

r = Phone(phone_name='Nokia', key_name='first')
r.put()

k = db.Key.from_path('Phone', 'first')

r = db.get(k)

On the whole, however, I have found that relying on auto-generated IDs is usually a better solution than specifying your own key names. Is there a particular reason you’re doing the latter?