How to pass complex objects across view functions/sessions in Flask

Question

I am writing a web application that receives a lot of data from a third party server, when (and only when) a user logs in. This data is parsed to custom objects and stored in a list(). Now the user works with this data all around the application, calling different views (e.g. sending different requests). I'm not sure what's the best pattern to pass the list of objects between the view functions?

I technically see two possibilities, but both have drawbacks in my case:

1. The session dict: Storing the data in the session is an overkill (the whole list would be send back and forth between server and browser on every request)
2. Persisting: Temporarly persisting the data to a database seem more adequate. But I was hoping to not having to use a database at all (except for this temporarly data I don't have any data that needs to be stored locally. Everything else is received from the third party server and sent back to it).

I'm not a very expirienced web developer, so maybe I oversee the obvious. So is there another way to pass the data between requests? Maybe some built in flask magic or is persisting (to a file or database) really the only option?

Answer 1

Although Flask's default implementation for sessions is to store the data in a cookie, that's not the only way to do it. Typically, you store a session ID in the cookie, and the data itself is stored somewhere on the server and retrieved via that cookie.

Flask does provide you with an easy way of overriding the default session implementation, and there are various recipes around showing how to do that - here's an SO question that shows the outline.