Type Hints

Some functions accept numbers as arguments; others accept strings. Some return lists; others return dictionaries, booleans, or None.

When a program is small, you can usually remember the types of your variables. But as programs grow, it's easy to forget:

• Is level an int or a str?
• Does get_item() always return an item name (str), or sometimes None if it can't find one?
• Is inventory a list of strings, or a dictionary of item counts?

Type hints let us write those expectations directly in our code:

def get_damage(weapon: dict, level: int) -> int:
    return weapon["damage"] + (level * 2)

The weapon: dict, level: int, and -> int parts are type hints. They tell humans and code editors what kinds of values the function expects and returns.

Type hints don't make Python stop being Python. It's still a dynamically typed language, and it won't automatically reject the wrong value just because a type hint says so.

Type hints are for:

• Making code easier to read
• Helping your editor autocomplete and warn you about mistakes
• Making bugs easier to spot before running your code