Type Hints Basics

This lesson covers the basics of Python's type hints, so you can understand a way of writing code whose intent is clearer. It's written for anyone searching "Python type hints tutorial".

Python is a dynamically typed language, but writing a "type hint," as in def add(a: int, b: int) -> int:, lets you make explicit what types a function accepts and what type it returns. It has no effect on execution, but it makes code easier to read and helps your editor's autocomplete and error checking.

The sample code adds an int type hint to the add function's parameters and return value, and a str type hint to the greet function. Because type hints are ignored at runtime, passing the wrong type doesn't itself raise an error — but your editor will show a warning.

A common beginner mistake is thinking type hints are more than "an unenforced marker." Unlike some other languages' type systems, Python itself won't raise an error if you pass a value that violates a type hint. If you want stricter checking, you need a dedicated tool like mypy.

On a large team, type hints make a function's intent much easier to convey, helping prevent bugs caused by an unexpected type mismatch before they happen. Using type hints liberally has become a recent trend in real-world Python projects.