Python typing

• Union types: int | float
• Tuple: tuple[int, str]
• List: list[int]
• Function types
  • Callable[[int, str], bool]: int * str -> bool
  • Callable[[], bool]: No arg 'function' returning a bool
  • Callable[[int], None]: 'Function' accepting an int that doesn't return a value
  • Callable[..., int]: Function accepting any number of args and returning an int
• Unknown type: ~Any`

Final

• Value of variable shouldn't be allowed to change after this point
• Change allowed before though
• Static type checker only, interpreter doesn't care

This is not the same as typing.final.

More

• https://docs.python.org/3.13/library/typing.html#overload
• https://docs.python.org/3.13/library/typing.html#typing.Protocol
  • https://typing.readthedocs.io/en/latest/spec/protocol.html#protocols