In my opinion the best place to start is the tutorial on python.org, for whichever version of python (2 or 3) you are learning.

Python 2: https://docs.python.org/2/tutorial/index.html

Python 3: https://docs.python.org/3/tutorial/index.html

Also start browsing through the modules listing, so that you don't reinvent too many wheels:

Python 2: https://docs.python.org/2/py-modindex.html

Python 3: https://docs.python.org/3/py-modindex.html

And the answer to whether you should learn 2 or 3 is:

2, because there are still 3rd party tools that don't support 3. Or because your friends are using 2.

Unless you know you need 3.

Or if all your friends are using 3 (because that's where a lot of your help is going to come from).

https://wiki.python.org/moin/Python2orPython3

But it doesn't matter overly much. Unless it does, for your job, but then they'll tell you.