Type hints stop runtime errors before they reach production.

Python is dynamically typed. You can pass a string where an integer is expected, and the code will run until it crashes. In a web API, that crash means a 500 error for a client, a failed downstream service call, or a corrupted database record. Type hints do not enforce types at runtime. They document intent. They allow static analysis tools like mypy to catch mismatches before you deploy. This guide shows how to use basic types, Optional , Union , and TypedDict to make your API code robust.

Basic Types for Request Processing

API endpoints accept data from external sources. Without type hints, function signatures are opaque. A developer reading def process_payment(amount): does not know if amount is a string, an integer, or a float.…