memory-only keyring?

[Colin Davis]

I'm working on a project where I need to handle a good many keys - I don't want to keep them all in a keyring, since they aren't interchangeable.
Different users might have different keys.

In this app, just being able to decode a message using ANY key isn't suffient. I want to know that I can decode a message using THIS key.

In theory, I could create a new keyfile on each substantiation of a gpg object, but then I wouldn't know when to delete them, and it'd create a bunch of temp files.

Is there any way to tell gnupg-python to just have no keyfile at all, and only use the keys I specify/import?
Alternatively, is there anyway to specify a specific a key to decode with, and fail if I can't decode with that single key?
As a final fallback, is there a way to find out which key it DID decode with? decode(msg).fingerprint comes up blank..

Thanks for any advice!