Frameworks and Tools that Inspired FastAPI

Frameworks that Inspired FastAPI

Original article: https://fastapi.tiangolo.com/alternatives (author: tiangolo, creator of FastAPI). It discusses the inspirations behind FastAPI, compares it with alternative frameworks, and extracts lessons learned.

Django

Django is the most popular Python web framework, trusted for large systems like Instagram. It tightly integrates with relational databases (MySQL, PostgreSQL), making NoSQL back‑ends less straightforward.

Django REST Framework (DRF)

DRF adds flexible API building capabilities to Django and was the first framework to automatically generate API documentation, a feature that directly inspired FastAPI.

DRF’s author, Tom Christie, also created Starlette and Uvicorn, the foundations on which FastAPI is built.

Flask

Flask is a lightweight micro‑framework without built‑in database integration, offering simplicity and flexibility that allow easy use of NoSQL databases and modular extensions.

Its minimal routing system inspired FastAPI to become a micro‑framework that can mix and match tools as needed.

Requests

Requests is a widely used HTTP client library. FastAPI is not a replacement for Requests; instead, FastAPI often uses Requests internally.

Requests’ simple, intuitive design and sensible defaults influenced FastAPI’s API design.

<code>response = requests.get("http://example.com/some/url")</code>

FastAPI equivalent endpoint:

<code>@app.get("/some/url")
def read_url():
    return {"message": "Hello World"}</code>

Both use a similar pattern: requests.get(...) vs. @app.get(...) .

Swagger / OpenAPI

DRF’s automatic API docs led to the discovery of the Swagger specification (now OpenAPI). FastAPI adopts OpenAPI to provide standardized, auto‑generated documentation with UI tools such as Swagger UI and ReDoc.

Flask REST Frameworks – Marshmallow

Marshmallow provides data serialization and validation, converting Python objects to JSON and ensuring input types are correct. FastAPI adopted a similar approach using Pydantic.

FastAPI’s Core Dependencies

Pydantic

Pydantic uses Python type hints for data validation, serialization, and JSON‑Schema generation, offering performance advantages over Marshmallow and excellent editor support.

Starlette

Starlette is a lightweight ASGI framework offering high performance, WebSocket, GraphQL, background tasks, CORS, GZip, static files, and more. FastAPI builds on Starlette, inheriting all its capabilities.

Impressive performance

WebSocket support

GraphQL support

Background task handling

Startup/shutdown events

Test client based on Requests

CORS, GZip, static files, streaming responses

Session and cookie support

100% test coverage

100% type‑annotated codebase

Zero external dependencies

Uvicorn

Uvicorn is a fast ASGI server built on uvloop and httptools. It is the recommended server for running FastAPI applications, often combined with Gunicorn for multi‑process deployments.

Overall, FastAPI combines the best ideas from these projects: automatic documentation (DRF/Swagger), simple routing (Flask/Requests), type‑driven validation (Pydantic), and high‑performance async handling (Starlette/Uvicorn).