python-expert-best-practices-code-review

Python 3.14+ Expert Best Practices Simple, pragmatic, opinionated. Only what matters for writing production-grade python code. When to Apply Reference these guidelines when: Writing Python functions, classes, or modules Reviewing Python code for error handling issues Refactoring existing Python codebases Implementing data validation and API boundaries Optimizing error detection and debugging patterns Rule Categories by Priority Priority Category Impact Prefix 1 Error Handling CRITICAL dict- , operators- 2 Common Bugs CRITICAL-HIGH no-mutable- , no-generic- 3 Code Clarity HIGH-MEDIUM listcomp- , no-inline- 4 Code Style LOW avoid- , unnecessary- Quick Reference dict-required-keys - Use d[key] for required dictionary keys to fail fast with KeyError no-mutable-defaults - No mutable defaults in function/method parameters operators-return-notimplemented - Return NotImplemented for unsupported operand types and design + vs += intentionally no-generic-except - Avoid generic except clauses to prevent hiding unexpected errors listcomp-no-side-effects - List comprehensions must produce a value you use (no side-effect listcomps) no-inline-imports - Place all import statements at the top of the file avoid-explanatory-comments - Avoid unnecessary comments for self-documenting code unnecessary-else-blocks - Avoid unnecessary else blocks after return/break/continue statements How to Use Read individual rule files for detailed explanations and code examples: rules/dict-required-keys.md rules/no-mutable-defaults.md rules/operators-return-notimplemented.md rules/no-generic-except.md rules/listcomp-no-side-effects.md rules/no-inline-imports.md rules/avoid-explanatory-comments.md rules/unnecessary-else-blocks.md Each rule file contains: Brief explanation of why it matters When to use and when not to use the pattern Implementation requirements Incorrect code example with explanation Correct code example with explanation Additional context and references