Learn the concept
A reusable project needs a documented entry point, dependency declaration, and test command. A pyproject.toml file can describe project metadata and tooling, while a lock or pinned environment strategy improves reproducibility. Do not assume someone else has the same global packages installed.
A command-line interface should validate arguments and provide meaningful exit behavior. Use argparse for required values, help text, and type conversion rather than manually indexing sys.argv. Separate argument parsing from business logic.
Organize code by responsibility: parsing, domain transformations, adapters, and entry points. Keep sample data synthetic and small. A README should show a successful command and explain a failure case. Packaging is about making the software usable by another person, not only making it run on your laptop.
Run and inspect
import argparse
parser = argparse.ArgumentParser(description="Process document batches")
parser.add_argument("--limit", type=int, default=10)
args = parser.parse_args(["--limit", "3"])
assert args.limit == 3
Your exercise
Add a CLI to your document processor with input, output, and limit arguments. Test --help, a missing input, and an invalid limit.
Check your understanding
A fresh environment can follow the README and run the tests and one sample command.