If only wxPython were to be available for Python v3.1 then I would choose that. Because it isn't yet, I prefer v2.6 and use "from future import ...."
If you don't choose to use any libraries that require v2.6 or older right now, then I'd encourage the choice of v3.1. I'm hoping all libraries will run with v3.1 given enough time.
If you don't choose to use any libraries that require v2.6 or older right now, then I'd encourage the choice of v3.1. I'm hoping all libraries will run with v3.1 given enough time.