We will write all our projects using Python Version 3.6.3, which is the latest stable release of Python at the time of writing.
The Python download package and instructions for downloading for different platforms are available at https://www.python.org/downloads/release/python-363/.
The installer binaries for macOS X and the Windows platform are available at the aforementioned link.
If you are following along on Unix, Linux, or BSD, the following procedure will install Python from the source.
First, install tk8.6-dev and python3-tk packages on your computer using your applicable package manager. For instance, on Debian-based systems such as Ubuntu and Mint, run the following two commands from the Terminal:
sudo apt install ...