Skip to content

Level 5 / Project 07 - Resilient JSON Loader

Home: README

Learn Your Way

Read Build Watch Test Review Visualize Try
— This project — — Flashcards — Browser

Quick Recall: This project uses structured error handling and fallback logic. Before starting, make sure you can: write a try/except block that catches a specific exception and provides a useful default value instead of crashing (Level 1, Project 01 - Input Validator Lab).

Estimated time: 75 minutes

Focus

  • safe parsing with fallback behavior

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-5/07-resilient-json-loader
python project.py --input data/primary.json --fallback data/backup.json --output data/loaded_data.json
pytest -q

Expected terminal output

Loaded 3 records via primary
8 passed

Expected artifacts

  • data/loaded_data.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 --strict flag that fails immediately instead of trying fallbacks.
  2. Add repair support for JSON with single quotes instead of double quotes.
  3. Log a detailed report of which sources were tried, in order, and which succeeded.
  4. Re-run script and tests.

Break it (required) — Core

  1. Corrupt primary.json by adding a trailing comma and delete backup.json.
  2. Create a primary.json that is valid JSON but not a list (e.g. a plain string).
  3. Capture the first failing test or visible bad output.

Fix it (required) — Core

  1. Make try_repair_json handle the trailing-comma case and restore the data.
  2. Validate that loaded data is a list; wrap non-list data in a list with a warning.
  3. Add tests for repair and type-mismatch cases.
  4. Re-run until output and tests are deterministic.

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

Explain it (teach-back)

  1. Why does try_load_json return a tuple of (data, error) instead of raising?
  2. How does try_repair_json attempt to fix trailing commas?
  3. What is the fallback chain order and why does repair come last?
  4. Where do you see resilient loading in production (config servers, cached fallbacks)?

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.

← Prev Home Next →