Python Best Practices

Type Hints (3.12+ Syntax)

# Use built-in generics (3.9+), no need for typing.List, typing.Dict
def process_items(items: list[str]) -> dict[str, int]:
    return {item: len(item) for item in items}

# Union with | syntax (3.10+)
def find_user(user_id: int) -> User | None:
    ...

# Type parameter syntax (3.12+)
type Vector[T] = list[T]
type Matrix[T] = list[Vector[T]]

def first[T](items: list[T]) -> T:
    return items[0]