FastAPI

FastAPI is a web framework first released in 2018 for building HTTP-based service APIs in Python. It is used for building APIs with Python 3.8+ based on standard Python-type hints.

FastAPI is based on Pydantic and uses type hints to validate, serialize and deserialize data. It also automatically generates OpenAPI documentation for APIs built with it.

Pydantic
Pydantic is a data validation library for Python. While writing code in an IDE, Pydantic provides type hints for schema validation and serialization through type annotations.

Starlette
Starlette is a lightweight ASGI framework/toolkit, to support async functionality in Python.

Uvicorn
Uvicorn is a minimal low-level server/application web server for async frameworks, following the ASGI specification. Technically, it implements a multi-process model with one main process, which is responsible for managing a pool of worker processes and distributing incoming HTTP requests to them. The number of worker processes is pre-configured, but can also be adjusted up or down at runtime.

Example
The following code shows a simple web application that displays "Hello World!" when visited: