Should I start learning python2 or python3?

No, because what you learn will be irrelevant if you go to code in Python3. Learn Python3 because it will have more features and possibly be simpler than Python2

Well, I would suggest you learn both. Although Python 2 is older than 3, it is still the de facto standard amongst Python Devs. Python 2 will be supported until 2020. If you hope the develop before then, it is still a useful tool. Also, the updates in Python 3 aren't that dramatic. For Ex: Python 2: 8/5 returns an integer (1) unless you do 8/float(5) Python 3: 8/5 returns the floating point number (1.6)