Question

If I have an object with a reference property, will calling the .key() or .key().id() method on the reference property cause it to be retrieved from the data store? Or can I can I get the value from those without a request being triggered?

class MyObject(db.Model):
    reference = db.ReferenceProperty()

myObj = MyObject( reference = myOtherObject )
myObj.put()

# Will this retrieve the key without doing a get for the object?
temp1 = myObj.reference.key()

# What about this?
temp2 = myObj.reference.key().id()

Answer 1

Accessing the property from the model instance will de-reference it (it will be fetched):

# This will retrieve the key after doing a get for the object.
temp1 = myObj.reference.key()

To get the key without de-referencing, use:

# This will retrieve the key without doing a get for the object.
temp1 = MyObject.reference.get_value_for_datastore(myObj)

# Then you get the id...
temp2 = temp1.id()