“Once you have your code well-tested you are ready to begin porting your code to Python 3! But to fully understand how your code is going to change and what you want to look out for while you code, you will want to learn what changes Python 3 makes in terms of Python 2. Typically the two best ways of doing that is reading the “What’s New” doc for each release of Python 3 and the Porting to Python 3 book (which is free online). There is also a handy cheat sheet from the Python-Future project.” Official statement from Python.org Besides that, Several statements such as print, exec, and others have been changed. E.g: print ‘hello world’ # valid python 2 not in python 3 print (‘hello world’) # valid python 3 and later versions of python 2