XML processing in Python -- changing horses in mid-stream

[Tim Rowe]

I have a Python program that parses a test script written in XML and puts 
the test results to stdout in XML (with a different DOCTYPE).

I also have a Python program that takes the test result XML and processes 
it for graphical presentation.

Here's my challenge. If the second program were given a test script 
instead of results, I would like it to recognise the different doctype, 
run the tests and process the results all in one.

When my result parser spots a test script I should be able to pass the 
script to the test program via a pipe, put the results of the test through 
a new result parser, and copy anything relevant from the new result parser 
to the old one. But can I stop the old result parser parsing the rest of 
the test script?

I plan to use either expat or pyxie, whichever is easiest.

TIA.