Why use System.Runtime.Caching or System.Web.Caching Vs static variables?

Long time listener – first time caller. I am hoping to get some advice. I have been reading about caching in .net – both with System.Web.Caching and System.Runtime.Caching. I am wondering what additional benefits I can get vs simply creating a static variable with locking. My current (simple minded) caching method is like this:

Does static reference to HttpContext.Current.Session return same session for all users?

Is there room for issue in the following code in terms of multiple users of the same web application? I mean, I know that a purely static string will be shared across all sessions for a single ASP.NET application, but given that this explicitly refers to the Current.Session, even though it is static it seems like it would always refer to the session instance of the “current user.”

Instance variables vs. class variables in Python

I have Python classes, of which I need only one instance at runtime, so it would be sufficient to have the attributes only once per class and not per instance. If there would be more than one instance (which won’t happen), all instance should have the same configuration. I wonder which of the following options would be better or more “idiomatic” Python.