Python Best Practices

Guidelines for writing and reviewing Python. 75 rules across 8 categories, prioritized by impact.

A rule match is a signal, not a verdict. Most rules are design preferences for new code, not bugs to fix across the repo — check the rule's impact level before flagging in review or refactoring stable code.

Quick-reference lines are triggers, not licenses: before applying a rule as a review finding or a transformation, open the rule file and check its counter-signal — the marker-opened paragraph (**When ...** / **Scope:** / **Preserve ...**) saying when NOT to apply it.

When to Apply

• Writing new Python modules, functions, classes, or data models
• Reviewing code for correctness or type safety
• Refactoring patterns in code that's being edited anyway

Avoid applying these rules as a blanket sweep across stable code — the churn rarely pays off.

Impact Levels