Source: 📖 Effective Python item 90

How to use typing

You can add a type to any name in python with the syntax name: type for variables and -> type for return values.

def my_func(value: int, value2: int) -> int:
	return value + value2

def concat(a: str, b: str) -> str:
	return a + b

Typing can be used to avoid common bugs before runtime, particularly with callers of your API.