SlackBuildsOrg/python/python3

Python is an interpreted, interactive, object-oriented programming
language that combines remarkable power with very clear syntax.
Python's basic power can be extended with your own modules written in C
or C++.  Python is also adaptable as an extension language for existing
applications.

Python 3 (a.k.a. "Python 3000" or "Py3k") is a new version of the
language that is incompatible with the 2.x line of releases.  The
language is mostly the same, but many details, especially how built-in
objects like dictionaries and strings work, have changed considerably,
and a lot of deprecated features have finally been removed.  Also, the
standard library has been reorganized in a few prominent places.

It is safe to install this on a system which already has 2.x version of
Python.