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Level 0 / Project 15 - Level 0 Mini Toolkit

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Estimated time: 30 minutes

Focus

  • combine basics into one tiny utility

Why this project exists

Combine everything from Level 0 into one multi-tool CLI. Choose between word counting, duplicate detection, and string cleaning -- all in a single script. This capstone shows how small functions compose into larger programs.

Run (copy/paste)

Use <repo-root> as the folder containing this repository's README.md.

cd <repo-root>/projects/level-0/15-level0-mini-toolkit
python project.py --input data/sample_input.txt --tool all
pytest -q

Expected terminal output

=== Mini Toolkit (all) ===

  [wordcount] 5 lines, 18 words
  [duplicates] 2 duplicate lines found
  [clean] 5 lines cleaned

Output written to data/output.json
5 passed

Expected artifacts

  • data/output.json
  • Passing tests
  • Updated notes.md

Checkpoint: Baseline code runs and all tests pass. Commit your work before continuing.

Alter it (required) — Extension

  1. Add a fourth tool: "reverse" that reverses the order of lines in the file.
  2. Add an --all flag that runs every tool and combines results into one report.
  3. Re-run script and tests.

Break it (required) — Core

  1. Pass --tool unknown_tool -- does run_tool() raise ValueError with a helpful message?
  2. Use an empty file as input -- do all three tools handle it without crashing?
  3. Pass no --tool flag at all -- what is the default behaviour?

Fix it (required) — Core

  1. Ensure run_tool() raises ValueError listing the valid tool names.
  2. Handle empty-file input gracefully for each tool (return zero counts, empty list, unchanged string).
  3. Add a test for the unknown-tool error message.

Checkpoint: All modifications done, tests still pass. Good time to review your changes.

Explain it (teach-back)

  1. Why does run_tool() use an if/elif chain instead of a dict mapping tool names to functions?
  2. What does run_all_tools() demonstrate about combining small functions into larger workflows?
  3. Why is the --tool argument a choices list in argparse?
  4. Where would multi-tool CLIs appear in real software (git, docker, kubectl)?

Mastery check

You can move on when you can: - run baseline without docs, - explain one core function line-by-line, - break and recover in one session, - keep tests passing after your change.

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