As you may have heard, I've spent some time at work working on an open source, language-agnostic a/b testing framework.
sixpack-web are built with Python and Werkzurg, with Redis as the primary datastore. It also make use of a little bit of Lua script for interacting with Redis.
Go ahead an browse the source at github.
We had originally planned to launch Sixpack several months ago, but decided to let it run in production to gather quite a bit more data. This turned out to be an incredible good idea, as it helped up to squash several more subtle, yet show-stopping bugs, such as bad robot detection, and some bugs related to sixpack-web and the client libraries.
hacker news discussion: here