python-expert-best-practices-code-review

SKILL.md

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