I cant really understand how youtube serves videos but I have been reading through what I can, it seems like the old method get_video is now obsolete and can\'t be used any more
You might have some luck with youtube-dl
http://rg3.github.com/youtube-dl/documentation.html
I'm not sure if there's a good API, but it's written in Python, so theoretically you could do something a little better than Popen :)