Basic

Without using a library.

if len(sys.argv) != 2:
    sys.stderr.write(f"Usage: {__file__} DIRECTORY\n")
    sys.exit(1)

The snippet I used set up the dynamic value as sys.argv[0]. The value of that will be like script name if running standalone as an install package. But if running as python app.py, it will be python`.

I used __file__ above - so you’ll have app.py. Or the full path.

Argparse