Hi Pierre, sounds neat! Two quick thoughts:
* The tor project generally dislikes other projects using the name 'tor' within them. This is why I called my projects arm and stem (arm was actually originally called tormoni, a name I still like a lot better)...
https://www.torproject.org/docs/trademark-faq.html.en
* Stem might be able to help you a great deal with this project. It's not just a client of tor's control port, but also a python implementation of its directory specification. For starters I'd look at its new remote descriptor fetching module to pull descriptor content...
https://stem.torproject.org/ https://stem.torproject.org/api/descriptor/remote.html
Best of luck! -Damian