As far as I know, Panda3D has no support for Python 3.x
I would highly advise you use Python 2.x (latest 2.x release)
Panda3D 2.0 (last I heard) would be designed with Python 3 in mind, meaning it will probably be an optional feature.
Also, most libraries outside the standard Python distribution, as well as every Panda3D sample currently, is written for Python 2.x
I too, would like to begin using Python 3.x, however I believe it to be more fact instead of opinion, in the sense that most older libraries are only for Python 2.x currently.
People appear to be slowly making a transition to Python 3, and surely you could use Python 3, you would have to recompile Panda3D, and possibly fix any issues that come with an upgrade to Python 3.
In short: (as far as I’m aware) Panda3D only supports Python 2.x currently. It’s advised you learn Python 2.x instead.
On a side note, Python 3 is still just as much Python as Python 2.x is, only some basic things have changed, it’s fairly easy to convert code (or write python 2.x code with support for python 3.x), google this for more information.
I hope I’ve helped any,
~powerpup118