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Level 2 / Project 08 - Mini Inventory Engine

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Concept This project — Quiz Flashcards Diagram Browser

Estimated time: 40 minutes

Focus

  • stock add/remove and reorder alerts

Why this project exists

This project gives you level-appropriate practice in a realistic operations context. Goal: run the baseline, alter behavior, break one assumption, recover safely, and explain the fix.

Run (copy/paste)

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

cd <repo-root>/projects/level-2/08-mini-inventory-engine
python project.py --inventory data/sample_input.txt
python project.py --inventory data/sample_input.txt --low-stock
python project.py --inventory data/sample_input.txt --value
python project.py --inventory data/sample_input.txt --search "key"
pytest -q

Expected terminal output

Inventory (10 products):
  bolt: qty=500, $0.50, hardware
  ...
12 passed

Expected artifacts

  • Inventory listing on stdout
  • 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 --remove command: --remove "Widget" 5 to decrease stock.
  2. Add an --export flag that writes current inventory to a new CSV.
  3. Add a --category filter to show only items in a specific category.

Break it (required) — Core

  1. Add an item with negative quantity — is it allowed?
  2. Remove exactly all stock of an item — does it stay at 0 or get deleted?
  3. Load a CSV with non-numeric price values — what happens?

Fix it (required) — Core

  1. Add validation that quantity and price must be non-negative.
  2. Decide and document what happens when stock reaches 0.
  3. Handle CSV parsing errors with try/except and skip bad rows.

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

Explain it (teach-back)

  1. Why is the inventory stored as a dict-of-dicts instead of a list?
  2. How does dict.get(key, default) help avoid KeyError?
  3. What is the difference between mutating a dict vs returning a new one?
  4. Where would this pattern be used in a real e-commerce system?

Mastery check

You can move on when you can: - implement add/remove/search from memory, - explain how nested dicts model real-world entities, - add a new feature (e.g. price history) without breaking existing code, - describe why the function returns a result dict instead of raising exceptions.

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