Haddock is a framework for easily creating APIs. It uses Python and Twisted, and supports both CPython 2.7 and PyPy.
Haddock revolves around versions - it is designed so that you can write code for new versions of your API without disturbing old ones. You simply expand the scope of the unchanged methods, and copy a reference into your new version.
Long-form documentation can be found here.
Because I liked the look of Praekelt's Aludel but it didn't kind of work how I thought it would. So, I wrote something similar!
You need two things - the API description document, and the implementation.
You can find the example description document and the example Python in the root directory. Simply run example.py and navigate to this example endpoint for a demonstration.