websockets is a library for building WebSocket servers and clients in Python with a focus on correctness and simplicity.

Built on top of asyncio, Python's standard asynchronous I/O framework, it provides an elegant coroutine-based API.

Here's a client that says "Hello world!":

#!/usr/bin/env python

import asyncio
import websockets

async def hello(uri):
    async with websockets.connect(uri) as websocket:
        await websocket.send("Hello world!")

asyncio.get_event_loop().run_until_complete(
    hello('ws://localhost:8765'))

And here's an echo server (for Python ≥ 3.6):

#!/usr/bin/env python

import asyncio
import websockets

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

asyncio.get_event_loop().run_until_complete(
    websockets.serve(echo, 'localhost', 8765))
asyncio.get_event_loop().run_forever()

Does that look good? Start here.

The development of websockets is shaped by four principles:

1. Simplicity: all you need to understand is msg = await ws.recv() and await ws.send(msg); websockets takes care of managing connections so you can focus on your application.
2. Robustness: websockets is built for production; for example it was the only library to handle backpressure correctly before the issue became widely known in the Python community.
3. Quality: websockets is heavily tested. Continuous integration fails under 100% branch coverage. Also it passes the industry-standard Autobahn Testsuite.
4. Performance: memory use is configurable. An extension written in C accelerates expensive operations. It's pre-compiled for Linux, macOS and Windows and packaged in the wheel format for each system and Python version.

Documentation is a first class concern in the project. Head over to Read the Docs and see for yourself.

Professional support is available if you — or your company — are so inclined. Get in touch.

(If you contribute to websockets and would like to become an official support provider, let me know.)

• If you prefer callbacks over coroutines: websockets was created to provide the best coroutine-based API to manage WebSocket connections in Python. Pick another library for a callback-based API.
• If you're looking for a mixed HTTP / WebSocket library: websockets aims at being an excellent implementation of 6455: The WebSocket Protocol and 7692: Compression Extensions for WebSocket. Its support for HTTP is minimal — just enough for a HTTP health check.
• If you want to use Python 2: websockets builds upon asyncio which only works on Python 3. websockets requires Python ≥ 3.4.

Bug reports, patches and suggestions welcome! Just open an issue or send a pull request.

websockets is released under the BSD license.