Overview
Twisted provides a variety of implementations of the twisted.internet.reactor. The specialized
implementations are suited for different purposes and are
designed to integrate better with particular platforms.
The select()-based reactor is Twisted's cross-platform reactor.
Platform-specific reactor implementations exist for:
- Poll for Linux
- Epoll for Linux 2.6
- WaitForMultipleObjects (WFMO) for Win32
- Input/Output Completion Port (IOCP) for Win32
- KQueue for FreeBSD and Mac OS X
- CoreFoundation for Mac OS X
The remaining custom reactor implementations provide support for integrating with the native event loops of various graphical toolkits. This lets your Twisted application use all of the usual Twisted APIs while still being a graphical application.
Twisted currently integrates with the following graphical toolkits:
When using applications that are runnable using twistd, e.g.
TACs or plugins, there is no need to choose a reactor explicitly, since
this can be chosen using twistd's -r option.
In all cases, the event loop is started by calling reactor.run(). In all cases, the event loop
should be stopped with reactor.stop().
IMPORTANT: installing a reactor should be the first thing
done in the app, since any code that does
from twisted.internet import reactor will automatically
install the default reactor if the code hasn't already installed one.
Reactor Functionality
| Status | TCP | SSL | UDP | Threading | Processes | Scheduling | Platforms | |
|---|---|---|---|---|---|---|---|---|
| select() | Stable | Y | Y | Y | Y | Y | Y | Unix, Win32 |
| poll | Stable | Y | Y | Y | Y | Y | Y | Unix |
| WaitForMultipleObjects (WFMO) for Win32 | Experimental | Y | Y | Y | Y | Y | Y | Win32 |
| Input/Output Completion Port (IOCP) for Win32 | Experimental | Y | Y | Y | Y | Y | Y | Win32 |
| CoreFoundation | Unmaintained | Y | Y | Y | Y | Y | Y | Mac OS X |
| epoll | Stable | Y | Y | Y | Y | Y | Y | Linux 2.6 |
| GTK+ | Stable | Y | Y | Y | Y | Y | Y | Unix, Win32 |
| wx | Experimental | Y | Y | Y | Y | Y | Y | Unix, Win32 |
| kqueue | Experimental | Y | Y | Y | Y | Y | Y | FreeBSD |
General Purpose Reactors
Select()-based Reactor
The select reactor is currently the default reactor on all
platforms. The following code will install it, if no other reactor has
been installed:
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from twisted.internet import reactor
In the future, if another reactor becomes the default, but the
select reactor is desired, it may be installed via:
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from twisted.internet import selectreactor selectreactor.install() from twisted.internet import reactor
Platform-Specific Reactors
Poll-based Reactor
The PollReactor will work on any platform that provides select.poll. With larger numbers of connected
sockets, it may provide for better performance than the SelectReactor.
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from twisted.internet import pollreactor pollreactor.install() from twisted.internet import reactor
KQueue
The KQueue Reactor allows Twisted to use FreeBSD's kqueue mechanism for
event scheduling. See instructions in the twisted.internet.kqreactor's
docstring for installation notes.
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from twisted.internet import kqreactor kqreactor.install() from twisted.internet import reactor
WaitForMultipleObjects (WFMO) for Win32
The Win32 reactor is not yet complete and has various limitations and issues that need to be addressed. The reactor supports GUI integration with the win32gui module, so it can be used for native Win32 GUI applications.
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from twisted.internet import win32eventreactor win32eventreactor.install() from twisted.internet import reactor
Input/Output Completion Port (IOCP) for Win32
Windows provides a fast, scalable event notification system known as IO Completion Ports, or IOCP for short. Twisted includes a reactor based on IOCP which is nearly complete.
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from twisted.internet import iocpreactor iocpreactor.install() from twisted.internet import reactor
Epoll-based Reactor
The EPollReactor will work on any platform that provides
epoll, today only Linux 2.6 and over. The
implementation of the epoll reactor currently uses the Level Triggered
interface, which is basically like poll() but scales much better.
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from twisted.internet import epollreactor epollreactor.install() from twisted.internet import reactor
GUI Integration Reactors
GTK+
Twisted integrates with PyGTK version
2.0 using the gtk2reactor. An example Twisted application that
uses GTK+ can be found
in doc/core/examples/pbgtk2.py.
GTK-2.0 split the event loop out of the GUI toolkit and into a separate
module called glib
. To run an application using the glib event loop,
use the glib2reactor. This will be slightly faster
than gtk2reactor (and does not require a working X display),
but cannot be used to run GUI applications.
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from twisted.internet import gtk2reactor # for gtk-2.0 gtk2reactor.install() from twisted.internet import reactor
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from twisted.internet import glib2reactor # for non-GUI apps glib2reactor.install() from twisted.internet import reactor
wxPython
Twisted currently supports two methods of integrating wxPython. Unfortunately, neither method will work on all wxPython platforms (such as GTK2 or Windows). It seems that the only portable way to integrate with wxPython is to run it in a separate thread. One of these methods may be sufficient if your wx app is limited to a single platform.
As with Tkinter, the support for integrating Twisted with a wxPython application uses specialized support code rather than a simple reactor.
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from wxPython.wx import * from twisted.internet import wxsupport, reactor myWxAppInstance = wxApp(0) wxsupport.install(myWxAppInstance)
However, this has issues when running on Windows, so Twisted now comes with alternative wxPython support using a reactor. Using this method is probably better. Initialization is done in two stages. In the first, the reactor is installed:
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from twisted.internet import wxreactor wxreactor.install() from twisted.internet import reactor
Later, once a wxApp instance has
been created, but before reactor.run()
is called:
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from twisted.internet import reactor myWxAppInstance = wxApp(0) reactor.registerWxApp(myWxAppInstance)
An example Twisted application that uses wxPython can be found
in doc/core/examples/wxdemo.py.
CoreFoundation
Twisted integrates with PyObjC version 1.0. Sample applications using Cocoa and Twisted
are available in the examples directory under
doc/core/examples/threadedselect/Cocoa.
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from twisted.internet import cfreactor cfreactor.install() from twisted.internet import reactor
Non-Reactor GUI Integration
Tkinter
The support for Tkinter doesn't use a specialized reactor. Instead, there is some specialized support code:
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from Tkinter import * from twisted.internet import tksupport, reactor root = Tk() # Install the Reactor support tksupport.install(root) # at this point build Tk app as usual using the root object, # and start the program with "reactor.run()", and stop it # with "reactor.stop()".
PyUI
As with Tkinter, the support for integrating Twisted with a PyUI application uses specialized support code rather than a simple reactor.
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from twisted.internet import pyuisupport, reactor pyuisupport.install(args=(640, 480), kw={'renderer': 'gl'})
An example Twisted application that uses PyUI can be found in doc/core/examples/pyuidemo.py.