# Choosing a Reactor and GUI Toolkit Integration

## 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 general purpose reactor implementations are:

- The select()-based reactor
- The poll()-based reactor

Platform-specific reactor implementations exist for:

- cReactor for Unix
- Java
- Win32

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:

- GTK+
- Qt
- Tkinter
- WxPython

The support for GTK+, Java, and Qt is straightforward and simple through the use of specialized reactors.

## General Purpose Reactors

### Select()-based Reactor

The SelectReactor is the default reactor.

    from twisted.internet import reactor

The SelectReactor may be explicitly installed by:

    from twisted.internet import default
    default.install()

### 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
    pollreactor.install()

## Platform-Specific Reactors

### cReactor for Unix

The cReactor is a high-performance C implementation of the Reactor interfaces. It is currently experimental and under active development. Be sure to see the installation notes prior to using the cReactor.

    from twisted.internet import cReactor
    cReactor.install()

### Java

The Java Reactor allows Twisted to run under Jython. It does not currently support AWT or Swing integration.

    from twisted.internet import javareactor
    javareactor.install()

### Win32

The Win32 reactor is not yet complete and has various limitations and issues that need to be addressed. One of the limitations is that it doesn't yet support GUI events, so it is currently not very useful for GUI applications. Contributed improvements in this area are very welcome.

    from twisted.internet import win32eventreactor
    win32eventreactor.install()

## GUI Integration Reactors

### GTK+

Twisted integrates with PyGTK. Sample applications using GTK+ and Twisted are available in the Twisted CVS.

    from twisted.internet import gtkreactor
    gtkreactor.install()

## Non-Reactor GUI Integration

### Qt

An example Twisted application that uses Qt can be found in doc/examples/qtdemo.py.

    from qt import QApplication
    app = QApplication([])

    from twisted.internet import qtsupport, reactor

    # make sure QT quits when twisted is stopped
    reactor.addSystemEventTrigger('after', 'shutdown', app.quit )

    # install QT support
    qtsupport.install(app)

    # run reactor
    reactor.run()

### Tkinter

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()
    root.withdraw()

    # Install the Reactor support
    tksupport.install(root)

    # Set up the interface here

    # Enter the Tk main loop
    mainloop()

An example Twisted application that uses Tk can be found in twisted/words/ui/tkim.py.

### WxPython

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 = MyWxApp(0)
    wxsupport.install(myWxAppInstance)
    reactor.run()

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