Python 3 was released in 2008 and is the way to go. Its not backwards compatible and many programs still use Python 2, but Python 3 is the present and the future.
If your Pi uses Python 2, you can install Python 3 safely as both can co-exist without problems. An alias can be created for the command python so that it uses Python 3 instead of 2.
Python 3 can be installed from apt. We will also install pip, a package manager to install and manage software packages written in Python.
sudo apt-get install python3
sudo apt-get install python-setuptools
sudo apt-get install python3-pip