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 for long polling, WebSockets, and other applications that require a long-lived connection to each user.
Here is a simple “Hello, world” example web app for Tornado:
import tornado.ioloop import tornado.web class MainHandler(tornado.web.RequestHandler): def get(self): self.write("Hello, world") application = tornado.web.Application([ (r"/", MainHandler), ]) if __name__ == "__main__": application.listen(8888) tornado.ioloop.IOLoop.current().start()
This example does not use any of Tornado’s asynchronous features; for that see this simple chat room.
pip install tornado
Tornado is listed in PyPI and
can be installed with
easy_install. 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 as well.
Manual installation: Download tornado-4.2.1.tar.gz:
tar xvzf tornado-4.2.1.tar.gz cd tornado-4.2.1 python setup.py build sudo python setup.py install
The Tornado source code is hosted on GitHub.
Prerequisites: Tornado runs on Python 2.6, 2.7, 3.2, 3.3, and 3.4. It
requires the certifi package
on all Python versions, and the backports.ssl_match_hostname package
on Python 2. These will be installed automatically when using
easy_install). Some Tornado features may
require one of the following optional libraries:
- unittest2 is needed to run Tornado’s test suite on Python 2.6 (it is unnecessary on more recent versions of Python)
- concurrent.futures is the
recommended thread pool for use with Tornado and enables the use of
ThreadedResolver. It is needed only on Python 2; Python 3 includes this package in the standard library.
- pycurl is used by the optional
tornado.curl_httpclient. Libcurl version 7.18.2 or higher is required; version 7.21.1 or higher is recommended.
- Twisted may be used with the classes in
- pycares is an alternative non-blocking DNS resolver that can be used when threads are not appropriate.
- Monotime adds support for a monotonic clock, which improves reliability in environments where clock adjustments are frequent. No longer needed in Python 3.3.
Platforms: Tornado should run on any Unix-like platform, although
for the best performance and scalability only Linux (with
and BSD (with
kqueue) are recommended for production deployment
(even though Mac OS X is derived from BSD and supports kqueue, its
networking performance is generally poor so it is recommended only for
development use). Tornado will also run on Windows, although this
configuration is not officially supported and is recommended only for
This documentation is also available in PDF and Epub formats.
- User’s guide
- Web framework
- HTTP servers and clients
- Asynchronous networking
- Coroutines and concurrency
- Integration with other services
tornado.auth— Third-party login with OpenID and OAuth
tornado.wsgi— Interoperability with other Python frameworks and servers
tornado.platform.asyncio— Bridge between
tornado.platform.caresresolver— Asynchronous DNS Resolver using C-Ares
tornado.platform.twisted— Bridges between Twisted and Tornado
tornado.autoreload— Automatically detect code changes in development
tornado.log— Logging support
tornado.options— Command-line parsing
tornado.stack_context— Exception handling across asynchronous callbacks
tornado.testing— Unit testing support for asynchronous code
tornado.util— General-purpose utilities
- Frequently Asked Questions
- Release notes
- 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
- What’s new in Tornado 4.2.1
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.
This web site and all documentation is licensed under Creative Commons 3.0.