Download and Install Python at this link: https://www.python.org/downloads/
On Mac/Linux, it's likely already installed, or you could use the command line if you're comfortable with it.
Fast and Easy for Demo Purposes
Go to this website and search for Python as the language: https://repl.it/
Or just use the command line on Mac/Linux if you are familiar.
Slower but better
Install some sort of Python IDE