[Tutor] Python persistent webserver?

[Howard Kao]

Hi all,

I know the subject is confusing but I don't know how to describe what
I would like to ask concisely.

Basically I would like to have a program (or server or whatever) take
an HTTP POST method (which contains some information, maybe even an
XML file) from a client, process these XML/information, and then
generate an XML to send back to the client.

Currently the environment it has to be done under is Apache on Linux. 
I am thinking that it may have to be a persistent running program... 
However it seems a daunting task for a Python noob like me.

Preferably it doesn't need threading and need not to be sophiscated at
all, as long as it can take the request, process info and send stuff
back to a client.

I have no idea how to do this at all and couldn't find much
information.  The Base, Simple, CGI HTTPServer modules all seem a
little lacking , but that's probably due to my lack of py-fu to start
with...   Any suggestions would be appreciated.  Many thanks!