What are Python type annotations and their compatibility?

What are Python type annotations and how do they work?

Python type annotations are a way to indicate the expected data types of variables, function parameters, and return values. They help with code readability and can be checked by static type checkers.

Are type annotations compatible with older versions of Python?

Type annotations were introduced in Python 3.5. While they won't cause errors in older versions, those versions won't recognize them, so it's best to use Python 3.5 or later for full compatibility.

Can I use type annotations in my existing codebase?

Yes, you can gradually add type annotations to your existing codebase. Start with function signatures and then expand to variables as needed.

What tools can help me check type annotations?

You can use tools like mypy, Pyright, or Pyre to check type annotations in your Python code.