writing-python

Type hints without Any enforce concrete types throughout your codebase. This Skill prescribes replacing Any with explicit Protocol-based types and stdlib alternatives, catching type errors early and making code intent clearer for maintenance and testing.

Use guard clauses and early returns to eliminate nested conditions, keeping functions flat and readable. This Skill guides you through Protocol-based dependency injection, pattern matching for control flow, and stdlib-first tooling like Typer to build maintainable CLI applications.

Guard clauses exit early when conditions fail, reducing indentation and nesting depth to a maximum of two levels. This Skill teaches you to replace deep conditionals with explicit error handling and early returns, making functions testable and easier to follow.

Protocols enable structural typing and dependency injection without inheritance constraints, aligning with modern Python 3.14+ patterns. This Skill enforces Protocol-based design over ABC to reduce coupling and support cleaner, more flexible service layer implementations.

Ruff for linting, mypy for static type checking, and pytest for testing form the modern Python quality stack. This Skill prescribes configuring these tools to enforce idiomatic patterns, guard clauses, explicit error handling, and stdlib-first solutions automatically.

Custom exception hierarchies enable explicit error handling and recovery paths specific to your domain. This Skill requires defining and raising custom exceptions rather than relying on built-in ones, improving clarity about failure modes in services, CLI tools, and scripts.