WSDL and XML generation

[guitarzero]

Hi all
Newbie in Python, i am looking for some pointers (or better existing
modules) to do the followings:

- generate (correct) XML messages from a WSDL file
- make some modifications inside XML messages *before* sending them to
the server hosting the Web services (described by previously
mentionned WSDL file)
- parse the answer.

Some ideas ?
Thanks in advance
Stephane