I'd like to integrate a web site written in Python (using Pylons) with an existing SAML based authentication service.  From reading about SAML, I believe that the IdP (which already exists in this scenario) will send an XML document (via browser post) to the Service Provider (which I am implementing).  The Service Provider will need to parse this XML and verify the identity of the user.
Are there any existing Python libraries that implement this functionality?
Thank you,
I know you are looking for a Python based solution but there are quite a few "server" based solutions that would potentially solve your problem as well and require few ongoing code maintenance issues. 
For example, using the Apache or IIS Integration kits in conjunction with the PingFederate server from www.pingidentity.com would allow you to pretty quickly and easily support SAML 1.0, 1.1, 2.0, WS-Fed and OpenID for your SP Application.
Hope this helps
Implementing a SAML client in Python