Austin Z. Henley Associate Teaching Professor Carnegie Mellon University 8/31/2025 Have you ever wondered how type checking works? Me too—let's make one! Python allows optional type annotations like this: def foobar(name: str | None) -> str: return "Fizz!" buzz: int = 42 A type checker goes through the code to make sure that the kinds of values you use match what your functions and variables expect. In the example above, it would check if foobar always returns a str. Type checking can catch erro...