In this chapter, we looked at how to use argparse and os.environ to gather command-line argument and configuration parameters. This builds on the techniques shown in Chapter 14, Configuration Files and Persistence.

We learned how to implement a number of common command-line features using argparse. This includes common features, such as showing the version number and exiting or showing the help text and exiting.

We looked at using the Command design pattern to create applications that can be expanded or refactored to offer new features. Our goal is to explicitly keep the body of the top-level main function as small as possible.