Re: Introspecting expressions in py3k
David Binger's talk was likely on Spec, a module which can be found in the QP web framework and in the Dulcinea package (a bolt on library of objects and UI suitable for QP or Quixote programmers).
Spec is useful enough all on its own. Its a single file, easy to comprehend, and once you start designing objects with it, you don't want to go back.
Its useful to look at some code that uses Spec - perhaps one of the Dulcinea objects like User or Item.