26. Type hints

Type hints document expected types without being enforced at runtime by the interpreter itself; tools like `mypy` check them statically.

python
from typing import Optional

def get_balance(address: str) -> float:
    return 0.0

def find_user(id: int) -> Optional[dict]:
    return None

Balances = dict[str, float]   # type alias (Python 3.9+)

Since Python 3.9, built-in generics (`list[int]`, `dict[str, int]`) work directly without importing from `typing`. Hints improve editor autocompletion and catch bugs before runtime, but Python remains dynamically typed regardless.

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