python-type-safety

npx skills add wshobson/agents --skill python-type-safety --agent claude-code

Same command for any agent — swap --agent for codex, cursor, copilot.

# Python Type Safety Leverage Python's type system to catch errors at static analysis time. Type annotations serve as enforced documentation that tooling validates automatically. ## When to Use This Skill - Adding type hints to existing code - Creating generic, reusable classes - Defining structural interfaces with protocols - Configuring mypy or pyright for strict checking - Understanding type narrowing and guards - Building type-safe APIs and libraries ## Core Concepts ### 1. Type Annotations Declare expected types for function parameters, return values, and variables. ### 2. Generics Write reusable code that preserves type information across different types. ### 3. Protocols Define structural interfaces without inheritance (duck typing with type safety). ### 4. Type Narrowing Use guards and conditionals to narrow types within code blocks. ## Quick Start ```python def get_user(user_id: str) -> User | None: """Return type makes 'might not exist' explicit.""" ... # Type checker enforces handling None case user = get_user("123") if user is None: raise UserNotFoundError("123") print(user.name) # Type checker knows user is User here ``` ## Fundamental Patterns ### Pattern 1: Annotate