Python 3.14+ Expert Best Practices

When to Apply

• 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

dict-

operators-

no-mutable-

no-generic-

listcomp-

no-inline-

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

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

• 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