I am really new to Python and I have been looking for an example on how to write a Web Service (XML - SOAP) in Python with Google App Engine with no luck.
Can anyone point me to an article or give me an example on how to do this?
I was curious about this myself and not finding anything I decided to try to get something to work. The short answer is that it turns out a SOAP service can actually be done using the latest alpha ZSI library. However it isn't simple and I didn't do much more than a simple request so it could fall apart with a complex type. I'll try to find time to write a tutorial on how to do it and edit this answer with more detail.
Unless this is a hard requirement I would do what jamtoday says and go with a REST or RPC service. The SOAP way could be filled with trouble.
Update: For anyone interested I've written a tutorial on how to deploy a SOAP service to the Google App Engine. It is long process so I'm just linking to it instead of pasting it all here.