Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed.
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.instance().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 pip or 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 the latest source from PyPI.
tar xvzf tornado-$VERSION.tar.gz cd tornado-$VERSION 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, and 3.3. It has no strict dependencies outside the Python standard library, although some features may require one of the following 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 tornado.netutil.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 tornado.platform.twisted.
- 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 epoll) and BSD (with kqueue) are recommended (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).
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