WebSockets in Python Without the Headaches

If you've ever tried to bolt real-time communication onto a Python app, you know the drill: you start with polling, it gets ugly, you reach for WebSockets, and suddenly you're drowning in connection lifecycle management. The websockets library exists to make that part boring—in the best way possible.

What It Does

websockets is a Python library for building WebSocket servers and clients, with a stated focus on correctness, simplicity, robustness, and performance. It's built on top of asyncio, Python's standard asynchronous I/O framework, and the default implementation gives you a coroutine-based API that feels natural if you've written async Python before.

What's notable is that asyncio isn't your only option. The library also ships implementations on top of threading and trio, plus a Sans-I/O layer for integrating WebSocket handling into third-party projects. That last piece matters if you're working with a framework that has its own event loop or networking model and you just need the protocol logic without the I/O opinions.

The core API is deliberately small. On the server side, you write an async function that receives a connection and loops over incoming messages. On the client side, you connect, send, and receive. The library handles the connection management so you can focus on your application logic.

Why It's Cool

The API is genuinely minimal. The README sums it up as "all you need to understand is msg = await ws.recv() and await ws.send(msg)." That's not marketing—that's basically the whole surface area for day-to-day use. Here's a complete echo server:

import asyncio
from websockets.asyncio.server import serve

async def echo(websocket):
    async for message in websocket:
        await websocket.send(message)

async def main():
    server = await serve(echo, "localhost", 8765)
    await server.serve_forever()

asyncio.run(main())

That's it. No decorators, no router registration, no config object. If you've spent time with heavier web frameworks, the contrast is refreshing.

It takes the RFC seriously. The library is heavily tested for compliance with RFC 6455, and continuous integration fails if branch coverage drops below 100%. That's an unusually strict bar, and it tells you something about how the maintainers think about correctness. WebSocket implementations have a reputation for subtle bugs around framing, close handshakes, and edge cases—this project treats those as first-class concerns rather than afterthoughts.

Backpressure was handled before it was cool. According to the README, websockets was the only library handling backpressure correctly before the issue became widely known in the Python community. If you've ever had a fast producer overwhelm a slow consumer and watched memory balloon, you know why this matters. It's the kind of thing you don't appreciate until it bites you in production.

You're not locked into one concurrency model. The threading API is a good example. If you're working in a synchronous codebase and don't want to restructure everything around asyncio, you can write this:

from websockets.sync.client import connect

def hello():
    with connect("ws://localhost:8765") as websocket:
        websocket.send("Hello world!")
        message = websocket.recv()
        print(f"Received: {message}")

hello()

The context manager handles cleanup, the calls are blocking, and it reads like ordinary Python. For scripts, small tools, or gradual migrations, that's a real convenience.

Performance is a consideration, not an afterthought. Memory usage is optimized and configurable, and a C extension accelerates expensive operations. It's pre-compiled for Linux, macOS, and Windows and packaged in wheels for each system and Python version—so you're not compiling anything at install time.

How to Try It

1. Install from PyPI:

pip install websockets

1. Write a minimal echo server using the asyncio API (see the snippet above) and run it.

2. In a separate terminal, connect with the threading client:

from websockets.sync.client import connect

with connect("ws://localhost:8765") as websocket:
    websocket.send("Hello world!")
    print(websocket.recv())

1. If you want a guided walkthrough, the project points to a tutorial in its documentation.

The repository lives at github.com/python-websockets/websockets, and the full docs are on Read the Docs.

Final Thoughts

websockets isn't trying to be a framework. It's a focused library that does one thing—WebSocket protocol handling—and does it with an unusual amount of rigor. The multiple concurrency backends mean it can fit into more codebases than a purely asyncio-based option would, and the Sans-I/O layer gives framework authors something to build on.

If you're building a real-time feature in Python and you want to spend your time on your application rather than on protocol details, this is a sensible default. Start with the tutorial, write the echo server, and see how little code it takes.