the 2x and 3x has too many differences that using one instead of other is highly not recommended. AG library is built on 2x and depends on it. The reason 3x still works because of its backward compatibility, enables new users to avoid learning curves. If you've put both side by side thats ok, but replacing 2x for 3 will not work at some extent. Consider reinstalling 2x and repair the environmental variables (paths and libraries). You can keep 3 for testing.
Me too have little knowledge on python, but do try these sometime,
http://learnpythonthehardway.org/
http://shop.oreilly.com/product/9781565924642.do
http://net.tutsplus.com/tutorials/the-best-way-to-learn-python/
Google for more !