Click
Python composable command line interface toolkit
...Click in three points, arbitrary nesting of commands, automatic help page generation, supports lazy loading of subcommands at runtime. Comes with useful common helpers (getting terminal dimensions, ANSI colors, fetching direct keyboard input, screen clearing, finding config paths, launching apps and editors, etc.). Click actually implements its own parsing of arguments and does not use optparse or argparse following the optparse parsing behavior. Click is designed to be fun and customizable but not overly flexible.