Implementing session-like storage in python application
You seem to be very confused and fixated on "sessions" for some reasons, maybe because your background is in the web apps?
Any-who you don't need "sessions" because with desktop application you have no trouble telling who is using the software without needing some elaborate tools. You don't need server, you don't need authentication tools, you don't need anything - just store that user within your single application. That is all really - a variable within your application called "user" and maybe some interface at the boot to pick one from available users.
And if you need it to last between boots, just save it in a file and read from it.
I will keep it short. 
Can someone please point me in the right direction in:

How to authenticate users in native applications written in Python?

I know in web there are sessions, but I can't think of a way to implement authentication, that will 'live' for some time and on expiry I can logout the user?
EDIT:
I am referring to desktop type of apps, I am fairly happy with the implementation for Web based development in Twisted
EDIT 2
The application I am thinking about will not authenticate against a server, but a self-contained application, an example the idea is a Cash Register/Point of Sale (my idea is kinda different, but parts of the functionality is the same), in which I need to authenticate the cashier, so I can log the transactions processed by him/her, print name on receipt and etc. All will be based in one single machine, no server communication or anything