Python 2 versus Python 3

At the time of writing this, Python 2 and Python 3 are both actively used; Python 2 is still taught in many tutorials, and a large number of forum discussions and blog posts on Python refer to Python 2. All this can make it confusing for beginners to decide which version to learn first. The reason for the confusion is that the adoption rate of Python 3 was relatively slow so Python 2 has been maintained longer than planned. However, Python 2 is set to be discontinued in 2020, which means that the core team that develops Python will no longer make updates to Python 2.

As Python 2 is on its way out, I will use Python 3 for this book. Despite a small number of strong opinions either way, Python 3 really isn't all that different. There are some minor syntactical and functional differences, but it's easy to learn them if you find yourself needing to use Python 2. (I've included some links in the reference material about these differences.)