Why is this datastore querying by key returning None?

Question

1) When I perform this query:

contract_record = Contract(book_number = 42, initial_page = 420, final_page = 442)
contract_record.put()
contract_key = contract_record.key()
contract = db.GqlQuery("SELECT * FROM Contract WHERE __key__ = KEY('Contract', '$[contract_key]')").get()

The result is None. Why?

2) How to make this query not by the key, but the key_id? (something like this:

contract_id = contract_record.key().id()
contract = db.GqlQuery("SELECT * FROM Contract WHERE __key__ = KEY('Contract', '$[contract_id]')").get()

Thanks for any help!

Answer 1

What is '$[contract_key]' supposed to be? Are you trying to do some sort of string substitution here? That really isn't how it works. Perhaps you mean to use the %s operator?

In any case, I don't really understand why you insist on doing queries via GQL. The way to get an object by its key is directly with get:

contract = db.get(contract_key)

and for the key ID:

contract = Contract.get_by_id(id)

Answer 2

Maybe this is not the answer you are looking for, but you could try this:

contract_record = Contract(book_number = 42, initial_page = 420, final_page = 442)
contract_record.put()
contract_key = contract_record.key()
contract = db.get(contract_key)