Getting Started with FastAPI and uv: A Lightweight Python Web Framework Stack

FastAPI is a modern Python web framework that makes it easy to build APIs quickly and efficiently, with automatic documentation and strong type support. Combined with uv — a lightweight developer tool that wraps Python virtual environments and package management — it becomes even simpler to set up and maintain projects.

In this post, you’ll learn:

What FastAPI is
What uv is
How to set up and run a FastAPI project using uv and uvicorn
Where to find a full example on GitHub

What is FastAPI?

FastAPI is a modern, high-performance web framework for building APIs with Python 3.7+ based on standard Python type hints. It’s built on top of Starlette for web handling and Pydantic for data validation.

Why FastAPI?

🚀 Super-fast performance (comparable to NodeJS and Go)
📃 Automatic interactive API docs (Swagger and ReDoc)
🧠 Built-in validation using Python type hints
🔒 Easy integration of authentication and dependency injection

What is `uv`?

uv is a fast and modern Python package manager developed by Astral. It wraps around virtual environments and provides an easy command-line interface for installing packages, managing dependencies, and isolating your Python projects.

You can think of it as a faster and more intuitive alternative to pip, venv, and pip-tools — all in one.

Setting Up FastAPI with `uv`

Here’s a quick guide to spin up a FastAPI app using uv.

1. Create and activate your environment

uv venv
source .venv/bin/activate

2. Install FastAPI and a web server

uv pip install fastapi uvicorn

3. Create your app

Make a new file:

touch main.py

Edit main.py and add this code to your simple app:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello, FastAPI + uv!"}

4. Run your server

Start the development server using uvicorn:

uvicorn main:app --reload

Visit http://127.0.0.1:8000 to see the response, and check out the auto-generated docs at http://127.0.0.1:8000/docs or redoc documentation under http://127.0.0.1:8000/redoc.

Managing Packages

Install additional packages:

uv pip install somepackage anotherpackage

Freeze your dependencies:

uv pip freeze > requirements.txt

Reactivate if you run into ‘ModuleNotFoundError’ with:

source .venv/bin/activate

Reinstall from requirements.txt later with:

uv pip install -r requirements.txt

Full Example

You can find the full example project on GitHub here:
👉 GitHub Repository

FastAPI + uv is a powerful combo for building modern, fast, and maintainable APIs with minimal setup. Whether you’re prototyping or building production-ready services, this stack gets you moving quickly.