Flask: 'session' vs. 'g'?

Question

I'm trying to understand the differences in functionality and purpose between g and session. Both are objects to 'hang' session data on, am I right? If so, what exactly are the differences and which one should I use in what cases?

Answer 1

No, g is not an object to hang session data on. g data is not persisted between requests.

session gives you a place to store data per specific browser. As a user of your Flask app, using a specific browser, returns for more requests, the session data is carried over across those requests.

g on the other hand is data shared between different parts of your code base within one request cycle. g can be set up during before_request hooks, is still available during the teardown_request phase and once the request is done and sent out to the client, g is cleared.