Appendix: Quick Reference

Annotation	Description	Example
int, str, float, bool	Basic built-in types	age: int = 25
List[T], list[T]	List containing items of type T	scores: list[int]
Tuple[T, ...], tuple[T, ...]	Tuple with specified item types	coords: tuple[float, float]
Dict[K, V], dict[K, V]	Dictionary with keys K, values V	user_data: dict[str, int]
Set[T], set[T]	Set containing items of type T	tags: set[str]
Optional[T]	Type T or None	name: Optional[str]
Union[T1, T2] or T1 | T2	Either type T1 or T2	value: int | str
Callable[[Args], ReturnType]	Function types	adder: Callable[[int, int], int]
Literal["value"]	Specific literal values	mode: Literal["auto", "manual"]
Annotated[T, metadata]	Type T with additional metadata	UserID = Annotated[int, "primary key"]
NewType('Name', T)	New distinct type based on type T	UserId = NewType('UserId', int)
Protocol	Structural typing protocol	class Speaker(Protocol): ...

[Add links to introductions in book]

Term	Definition
Annotation	Explicit type declaration for variables, functions, or classes.
Duck Typing	Determining an object's suitability based on presence of methods/attributes
Generics	Type annotations parameterized by type variables.
Literal Types	Types representing specific literal values.
Protocol	Interface defined by structural compatibility, rather than explicit inheritance.
Stub Files	Files (.pyi) containing type annotations without implementations.
Type Alias	Simplified or descriptive alias for complex type annotations.
Type Checking	Verification of type consistency either statically or at runtime.
Type Narrowing	Refining variable types within specific control-flow branches.
Variance	Rules describing subtype relationships between generic types (covariant, contravariant).
Static Typing	Types checked before execution (compile-time).
Dynamic Typing	Types determined and checked during execution (runtime).
Covariance	Generic type that accepts subtypes as substitutes for its type parameter.
Contravariance	Generic type that accepts supertypes as substitutes for its type parameter.
Invariant	Generic type that requires exact type matches for its type parameters.