in doubt consider reading sol's guide on how to surive ludumdare. ludumdare is a 48 hour competition, but many things apply to pyweek nonetheless; http://sol.gfxile.net/ldsurvival.html
As someone who always gets distracted by getting the graphics working (even though i promise myself that "this is the last time, damn it") Id recommend going for simple graphics and simple gameplay!
Be sure to hang out in the IRC channel (#pyweek on freenode) to ensure maximum fun! (also, you'll be able to ask for help if you run into a snag)
Looking forward to seeing your entry :)