# Tornado — Python Async Web Framework and Networking Library

> Tornado is a Python web framework and asynchronous networking library originally developed at FriendFeed (acquired by Facebook). Non-blocking I/O, WebSockets, long polling, and thousands of simultaneous connections. One of the earliest async Python web frameworks.

## Install

Save in your project root:

## Quick Use

```bash
pip install tornado
```

```python
import tornado.ioloop
import tornado.web
import json

class AssetsHandler(tornado.web.RequestHandler):
    def get(self):
        self.write(json.dumps([{"repo": "react", "stars": 230000}]))

    def post(self):
        data = json.loads(self.request.body)
        self.set_status(201)
        self.write(json.dumps(data))

class WebSocketHandler(tornado.websocket.WebSocketHandler):
    connections = set()

    def open(self):
        self.connections.add(self)

    def on_message(self, msg):
        for conn in self.connections:
            conn.write_message(msg)

    def on_close(self):
        self.connections.discard(self)

app = tornado.web.Application([
    (r"/api/assets", AssetsHandler),
    (r"/ws", WebSocketHandler),
])

if __name__ == "__main__":
    app.listen(8888)
    tornado.ioloop.IOLoop.current().start()
```

## Intro

Tornado is a Python web framework and asynchronous networking library originally developed at FriendFeed (acquired by Facebook in 2009). One of the earliest non-blocking I/O frameworks for Python, Tornado is designed for long-lived connections like WebSockets, long polling, and server-sent events. Used at Facebook, Quora, and other high-concurrency applications.

- **Repo**: https://github.com/tornadoweb/tornado
- **Stars**: 22K+
- **Language**: Python
- **License**: Apache 2.0

## What Tornado Does

- **Non-blocking I/O** — event loop based
- **Web framework** — routing, templates, auth, XSRF
- **WebSocket** — native support
- **HTTP client** — async HTTP requests
- **Coroutines** — `async def` / `await` (modern) or `gen.coroutine` (legacy)
- **asyncio compatible** — integrates with Python asyncio loop

## Comparison

| Framework | Async Model | WebSocket | Era |
|---|---|---|---|
| Tornado | IOLoop (asyncio) | Built-in | 2009 |
| FastAPI | ASGI (asyncio) | Via Starlette | 2018 |
| Sanic | uvloop | Built-in | 2016 |
| aiohttp | asyncio | Built-in | 2014 |

## 常见问题 FAQ

**Q: 新项目还用 Tornado 吗？**
A: 新项目推荐 FastAPI 或 Starlette。Tornado 主要维护老项目或需要自定义 IOLoop 的场景。

## 来源与致谢 Sources

- Docs: https://www.tornadoweb.org
- GitHub: https://github.com/tornadoweb/tornado
- License: Apache 2.0

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Source: https://tokrepo.com/en/workflows/412ffd8f-3634-11f1-9bc6-00163e2b0d79
Author: AI Open Source