Python Mastery

How to use this skill

Read SKILL.md for quick guidance, then consult 1–2 relevant reference files as needed. Do NOT read all reference files at once. For simple tasks, the quick principles below may suffice.

Reference files — when to read each one

Quick principles

1. Explicit over implicit. Favor clarity over cleverness. Extract hard-to-read expressions into descriptively named helpers.
2. Follow PEP 8. lowercase_underscore for functions/variables, CapitalizedWord for classes, ALL_CAPS for constants. 4-space indent, lines ≤ 79 chars. Use black and ruff.
3. Use the right data structure. Dicts → lookups, sets → membership, lists → ordered sequences, tuples → fixed records, deques → queues, dataclasses → structured data.
4. Prefer composition over inheritance. Inherit only for true is-a relationships; otherwise compose or use mix-ins.
5. Write for the reader. Code is read far more than written. Use descriptive names, docstrings, type hints, and small focused functions.
6. Don't repeat yourself. Extract shared logic, but don't over-abstract — two occurrences may be coincidence, three is a pattern.
7. Errors should never pass silently. Use exceptions, not return codes. Catch specific exceptions. Keep try blocks short.
8. Test your code. Python defers nearly all checks to runtime. Automated tests are your compiler.
9. Encapsulate what varies. Isolate changing parts from stable parts — the foundation of good design.
10. Iterate toward good design. Well-designed code rarely emerges in one pass. Write, test, refactor, repeat. Backtracking is normal.