I still remember me thinking "wish this was python" the first time I got to play with Avisynth.
Just Awesome.
For directshow sources and whatnot, here's an example of what you can do with python:
https://gist.github.com/3549096
And that's just (the graph building) part of a python program I wrote to watch tv with my capture card, forcing the ffdshow filters in the graph.