Which Version of Python?

[Peter]

If your desire is to "learn" Python then I would stick to 2.7

My reasoning would be that there are still a significant number of packages that have not been ported to 3.x (and may never be ported). 

Not having looked at the changes in 3.x (so don't flame me! :-)), it would seem that anything you "learn" in 2.7 would be easily transferred "up" when and if you feel the need to go to 3.x, but in the meantime enjoy the better support of a greater range of packages that are still only 2.x compatible! i.e. learning (and using) features of 3.x could make it difficult to go "down" when/if you decide you really need to use a library that hasn't (and may never!) be ported to 3.x. For example, Graysons book on Python GUI programming is still one of the better Python GUI books (although very old now!) and it would steer you towards using the Pmw library - which may never be ported to 3.x. If you decide to use wxPython for your GUI work then I see that has support for 2.x only also.

So in this case, staying with the lower common denominator might be the better choice.