An important choice you're also faced with initially is... Do you want to get the default OpenStreetMap stylesheets working with Mapnik? We have a lot of documentation about how to do this. Unfortunately it's a little more fiddly than some of the basic "Getting started" Mapnik tutorials, and you are more restricted as to which Mapnik version you work with and what your data source types are.
To get the OSM *default* stylesheet running you *must* work with PostGIS (as well as some shapefiles for zoomed out world boundaries and coastline), and you *must* populate the database using osm2pgsql which is also governed by a matching style configuration file. Hopefully a good guide to all this is the [Mapnik][1] wiki page. Having done the database loading, there's some python scripts provided: generate_image.py `generate_image.py` and generate_tiles.py `generate_tiles.py` Playing around with these, you'll get some control within python, but it's not quite the same as the from-scratch tutorial you link to.
...but maybe there's a better half-way-house tutorial involving osm2pgsql and building style rules in python. (Anyone know?)
[1]: http://wiki.openstreetmap.org/wiki/Mapnik
