First of all, if you don’t have Python installed on your computer, download and install it from the Python official website now.
To make sure your Python is functional, type
python3 in a terminal window, or just
python if that does not work. Here is what you should expect to see:
Python 3.6.3 (v3.6.3:2c5fed86e0, Oct 3 2017, 00:32:08) [GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>>