Tornado Web Server — Tornado 6.4.2 documentation (original) (raw)

¶

Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. By using non-blocking network I/O, Tornado can scale to tens of thousands of open connections, making it ideal forlong polling,WebSockets, and other applications that require a long-lived connection to each user.

Quick links¶

• Current version: 6.4.2 (download from PyPI, release notes)
• Source (GitHub)
• Mailing lists: discussion and announcements
• Stack Overflow
• Wiki

Hello, world¶

Here is a simple “Hello, world” example web app for Tornado:

import asyncio import tornado

class MainHandler(tornado.web.RequestHandler): def get(self): self.write("Hello, world")

def make_app(): return tornado.web.Application([ (r"/", MainHandler), ])

async def main(): app = make_app() app.listen(8888) await asyncio.Event().wait()

if name == "main": asyncio.run(main())

This example does not use any of Tornado’s asynchronous features; for that see this simple chat room.

Threads and WSGI¶

Tornado is different from most Python web frameworks. It is not based on WSGI, and it is typically run with only one thread per process. See the User’s guidefor more on Tornado’s approach to asynchronous programming.

While some support of WSGI is available in the tornado.wsgi module, it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI.

In general, Tornado code is not thread-safe. The only method in Tornado that is safe to call from other threads isIOLoop.add_callback. You can also use IOLoop.run_in_executor to asynchronously run a blocking function on another thread, but note that the function passed to run_in_executor should avoid referencing any Tornado objects. run_in_executor is the recommended way to interact with blocking code.

asyncio Integration¶

Tornado is integrated with the standard library asyncio module and shares the same event loop (by default since Tornado 5.0). In general, libraries designed for use with asyncio can be mixed freely with Tornado.

Installation¶

Tornado is listed in PyPI and can be installed with pip. Note that the source distribution includes demo applications that are not present when Tornado is installed in this way, so you may wish to download a copy of the source tarball or clone the git repository as well.

Prerequisites: Tornado 6.3 requires Python 3.8 or newer. The following optional packages may be useful:

• pycurl is used by the optionaltornado.curl_httpclient. Libcurl version 7.22 or higher is required.
• pycares is an alternative non-blocking DNS resolver that can be used when threads are not appropriate.

Platforms: Tornado is designed for Unix-like platforms, with best performance and scalability on systems supporting epoll (Linux),kqueue (BSD/macOS), or /dev/poll (Solaris).

Tornado will also run on Windows, although this configuration is not officially supported or recommended for production use. Some features are missing on Windows (including multi-process mode) and scalability is limited (Even though Tornado is built on asyncio, which supports Windows, Tornado does not use the APIs that are necessary for scalable networking on Windows).

This documentation is also available in PDF and Epub formats.

• User’s guide

  • Introduction
  • Asynchronous and non-Blocking I/O
  • Coroutines
  • Queue example - a concurrent web spider
  • Structure of a Tornado web application
  • Templates and UI
  • Authentication and security
  • Running and deploying

• Web framework

  • tornado.web — RequestHandler and Application classes
  • tornado.template — Flexible output generation
  • tornado.routing — Basic routing implementation
  • tornado.escape — Escaping and string manipulation
  • tornado.locale — Internationalization support
  • tornado.websocket — Bidirectional communication to the browser

• HTTP servers and clients

  • tornado.httpserver — Non-blocking HTTP server
  • tornado.httpclient — Asynchronous HTTP client
  • tornado.httputil — Manipulate HTTP headers and URLs
  • tornado.http1connection – HTTP/1.x client/server implementation

• Asynchronous networking

  • tornado.ioloop — Main event loop
  • tornado.iostream — Convenient wrappers for non-blocking sockets
  • tornado.netutil — Miscellaneous network utilities
  • tornado.tcpclient — IOStream connection factory
  • tornado.tcpserver — Basic IOStream-based TCP server

• Coroutines and concurrency

  • tornado.gen — Generator-based coroutines
  • tornado.locks – Synchronization primitives
  • tornado.queues – Queues for coroutines
  • tornado.process — Utilities for multiple processes

• Integration with other services

  • tornado.auth — Third-party login with OpenID and OAuth
  • tornado.wsgi — Interoperability with other Python frameworks and servers
  • tornado.platform.caresresolver — Asynchronous DNS Resolver using C-Ares
  • tornado.platform.twisted — Bridges between Twisted and Tornado
  • tornado.platform.asyncio — Bridge between asyncio and Tornado

• Utilities

  • tornado.autoreload — Automatically detect code changes in development
  • tornado.concurrent — Work with Future objects
  • tornado.log — Logging support
  • tornado.options — Command-line parsing
  • tornado.testing — Unit testing support for asynchronous code
  • tornado.util — General-purpose utilities

• Frequently Asked Questions

• Release notes

  • What’s new in Tornado 6.4.2
  • What’s new in Tornado 6.4.1
  • What’s new in Tornado 6.4.0
  • What’s new in Tornado 6.3.3
  • What’s new in Tornado 6.3.2
  • What’s new in Tornado 6.3.1
  • What’s new in Tornado 6.3.0
  • What’s new in Tornado 6.2.0
  • What’s new in Tornado 6.1.0
  • What’s new in Tornado 6.0.4
  • What’s new in Tornado 6.0.3
  • What’s new in Tornado 6.0.2
  • What’s new in Tornado 6.0.1
  • What’s new in Tornado 6.0
  • What’s new in Tornado 5.1.1
  • What’s new in Tornado 5.1
  • What’s new in Tornado 5.0.2
  • What’s new in Tornado 5.0.1
  • What’s new in Tornado 5.0
  • What’s new in Tornado 4.5.3
  • What’s new in Tornado 4.5.2
  • What’s new in Tornado 4.5.1
  • What’s new in Tornado 4.5
  • What’s new in Tornado 4.4.3
  • What’s new in Tornado 4.4.2
  • What’s new in Tornado 4.4.1
  • What’s new in Tornado 4.4
  • What’s new in Tornado 4.3
  • What’s new in Tornado 4.2.1
  • What’s new in Tornado 4.2
  • What’s new in Tornado 4.1
  • What’s new in Tornado 4.0.2
  • What’s new in Tornado 4.0.1
  • What’s new in Tornado 4.0
  • What’s new in Tornado 3.2.2
  • What’s new in Tornado 3.2.1
  • What’s new in Tornado 3.2
  • What’s new in Tornado 3.1.1
  • What’s new in Tornado 3.1
  • What’s new in Tornado 3.0.2
  • What’s new in Tornado 3.0.1
  • What’s new in Tornado 3.0
  • What’s new in Tornado 2.4.1
  • What’s new in Tornado 2.4
  • What’s new in Tornado 2.3
  • What’s new in Tornado 2.2.1
  • What’s new in Tornado 2.2
  • What’s new in Tornado 2.1.1
  • What’s new in Tornado 2.1
  • What’s new in Tornado 2.0
  • What’s new in Tornado 1.2.1
  • What’s new in Tornado 1.2
  • What’s new in Tornado 1.1.1
  • What’s new in Tornado 1.1
  • What’s new in Tornado 1.0.1
  • What’s new in Tornado 1.0

• Index

• Module Index

• Search Page

Discussion and support¶

You can discuss Tornado on the Tornado developer mailing list, and report bugs on the GitHub issue tracker. Links to additional resources can be found on the Tornado wiki. New releases are announced on the announcements mailing list.

Tornado is available under the Apache License, Version 2.0.

This web site and all documentation is licensed under Creative Commons 3.0.