Looking at the Mapnik Python docs it indeed looks nice!
So I'm all for it - if you can port it (and its dependencies), I'm sure I can make it show something usable in modRana.

Some possible concerns:

• dependencies - Mapnik seems to have quite a lot of dependencies (no problem if you can manage to package & build them all )
• scaling - the example in the docs is just rendering country borders, for normal usage in modRana a much higher level of detail is needed & for a much larger area
  • getting data - could be from Geofabrik or from other extract site
  • data access - IIRC Mapnik is using postgis (PostgreSQL with some geographic extensions, making it possible to query distinct regions easily) for data storage & access, so that might be another dependency that might be needed (or maybe Mapnik supports some other format more suitable for mobile use ?)
  • rendering speed - Mapnik servers are usually pretty beefy machines, but I would say with a simple enough style (like for example routes & route names only) we should hopefully get some usable rendering speed

Question backlog
As I'm as busy as always, while I follow the modRana thread I'm not always able to answer all questions right away - I'll try to do something about it in the next few days.