These files, as written, are aimed at command-line execution, but because if __name__ == '__main__':
only fires when run on the command line, it can also be included in another python script if need be.
It uses doctests (which fire when run from the command line with a -t
/ --test
flag) because I like doctests because they're the simplest way to add tests to your code, and tests in your code are a good way to help remind future-you how current-you imagined you'd be using the code you wrote.
The code you want to execute goes in the main() method.