Choosing a Reactor and GUI Toolkit Integration

  1. Overview
  2. Reactor Functionality
  3. General Purpose Reactors
  4. Platform-Specific Reactors
  5. GUI Integration Reactors
  6. Non-Reactor GUI Integration


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 general purpose reactor implementations are:

Platform-specific reactor implementations exist for:

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 runnable using twistd, e.g. TAPs 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 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 hasen't already installed one.

Reactor Functionality

select()StableYYYYYYUnix, Win32
Win32 (WFMO)ExperimentalYYYYYYWin32
Win32 (IOCP)ExperimentalYNNNNYWin32
CoreFoundationUnmaintainedYYYYYYOS X
GtkStableYYYYYYUnix, Win32
wxExperimentalYYYYYYUnix, Win32

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:

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:

from twisted.internet import selectreactor

Poll()-based Reactor

The PollReactor will work on any platform that provides poll(). With larger numbers of connected sockets, it may provide for better performance.

from twisted.internet import pollreactor

Platform-Specific Reactors


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.

from twisted.internet import kqreactor

Win32 (WFMO)

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.

from twisted.internet import win32eventreactor

Win32 (IOCP)

Windows provides a fast, scalable event notification system known as IO Completion Ports, or IOCP for short. An extremely experimental reactor based on IOCP is provided with Twisted.

from twisted.internet import iocpreactor

GUI Integration Reactors


Twisted integrates with PyGTK, versions 1.2 (gtkreactor) and 2.0 (gtk2reactor). Sample applications using GTK+ and Twisted are available in the Twisted SVN.

GTK-2.0 split the event loop out of the GUI toolkit, 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.

from twisted.internet import gtkreactor # for gtk-1.2
from twisted.internet import gtk2reactor # for gtk-2.0
from twisted.internet import glib2reactor # for non-GUI apps


Twisted integrates with PyObjC, version 1.0. Sample applications using Cocoa and Twisted are available in the examples directory under Cocoa.

from twisted.internet import cfreactor

Non-Reactor GUI Integration


The support for Tkinter doesn't use a specialized reactor. Instead, there is some specialized support code:

from Tkinter import *
from twisted.internet import tksupport

root = Tk()

# Install the Reactor support

# at this point build Tk app as usual using the root object,
# and start the program with "", and stop it
# with "reactor.stop()".


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.

from wxPython.wx import *
from twisted.internet import wxsupport, reactor

myWxAppInstance = wxApp(0)

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:

from twisted.internet import wxreactor

Later, once a wxApp instance has been created, but before is called:

myWxAppInstance = wxApp(0)

An example Twisted application that uses WxWindows can be found in doc/examples/


As with Tkinter, the support for integrating Twisted with a PyUI application uses specialized support code rather than a simple reactor.

from twisted.internet import pyuisupport, reactor

pyuisupport.install(args=(640, 480), kw={'renderer': 'gl'})

An example Twisted application that uses PyUI can bve found in doc/examples/


Version: 2.5.0