Using the latest features of Python 3
The latest version of the Python 2.x branch, Python 2.7, was released in 2010. It will reach its end of life in 2020. On the other hand, the first version of the Python 3.x branch, Python 3.0, was released in 2008. The decade-long transition period between Python 2 and Python 3, which are slightly incompatible, has been somewhat chaotic.
Choosing between Python 2 (also known as Legacy Python) and Python 3 used to be tricky since many Python users had not transitioned to Python 3 yet, and many libraries were only compatible with Python 2. Those times are gone and it is now safe to stick with Python 3 in virtually all cases. The only exceptions are when you have to support old unmaintained libraries, or when your users cannot transition to Python 3 for whatever reason.
In addition to fixing the bugs and annoyances of Python 2 (for example, related to Unicode support), Python 3 brings many interesting features in terms of syntax, capabilities of the language...