This Twisted thingy is seriously hard stuff to understand... In addition to that threading doc (post link), see howtos about deferreds and async programming.
What I'm trying to do here is plug Berkeley DB XML into a Twisted.Web2 application. This involves delegating DB access to worker threads outside the Twisted event loop ("reactor" pattern). A lot more stuff to figure out before coding starts...
sudo apt-get install python-twisted
sudo apt-get install python-twisted-web2
wget http://twistedmatrix.com/projects/web2/documentation/examples/intro/simple.py
twistd -ny simple.py
And then point your web browser to http://<server address>:8080 — and go tweak the code.
Twisted.Web2 docs can be found at: http://twistedmatrix.com/projects/web2/documentation/.
See the Wikipedia article for overview of Twisted.