> Choose Python 3 only if you need to and/or fully understand the implications.
I would apply the "if you need to" part to Python 2. "3 if you can, 2 if you must"
I would apply the "if you need to" part to Python 2. "3 if you can, 2 if you must"
Novice: "I want to do X" Internet advice: "Use package Y" Novice: "Okay <install, install>, wtf nothing is working" <long frustrating debugging session> Novice: "Oh, wow, this doesn't support Python3 yet. Now I have to ignore all the internet advice and forge my own path, OR port all my code back to 2.7! This language sucks!"
The alternative seems preferable: Stuff works, but occasionally you don't get a whiz-bang feature (you "only" get 2.7's feature set, poor you). Five years pass, you learn the language. Now you've gotta learn a bunch of new habits, which sucks, but it's not as bad because now you're pretty good at Python, so the easy parts are easy.
More and more questions have problems that can be solved by Python 3, but it's probably a pain in the ass if you start with 3 then work out how to solve your problem.
http://wiki.python.org/moin/Python2orPython3
tl;dr "If 3 does everything you need, great. However, there's a good bit of things that still don't work with 3, in which case 2 is the safer choice. Here's a pretty long list of reasons why 2 is probably better for you. ..."
But I bet within a year, that's no longer true. (This is dependent on package migration, but there's been a lot of progress lately, and the chances of a novice needing a sophisticated package day one is slim anyway.)
There are a few items that Python 3 fixes that will make this a no-brainer when the vast majority of major packages are ported to 3. Specifically, floating point results of integer division, and print as a function are two that come to mind.
I can't tell you how many times I cursed at the same bug as a beginner (back before division was importable from __future__). 1/2 + 1/2 = 0. Uggh!
And the beginner may as well get in the habit day 1 of using parentheses in statements like print("Hello World").
That said, I try to use any backported 3.0 features such as .format for string formatting. And for beginners, I heartily recommend using the 'six' module. That way when you need to move to 3.0, porting your code or your skills, will be easy-peasy.