<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <link rel="STYLESHEET" href="lib.css" type='text/css' /> <link rel="SHORTCUT ICON" href="../icons/pyfav.gif" /> <link rel='start' href='../index.html' title='Python Documentation Index' /> <link rel="first" href="lib.html" title='Python Library Reference' /> <link rel='contents' href='contents.html' title="Contents" /> <link rel='index' href='genindex.html' title='Index' /> <link rel='last' href='about.html' title='About this document...' /> <link rel='help' href='about.html' title='About this document...' /> <LINK rel="next" href="node645.html"> <LINK rel="prev" href="node643.html"> <LINK rel="parent" href="node637.html"> <LINK rel="next" href="node645.html"> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <meta name='aesop' content='information' /> <META name="description" content="Bindings and Events"> <META name="keywords" content="lib"> <META name="resource-type" content="document"> <META name="distribution" content="global"> <title>16.1.6.7 Bindings and Events</title> </head> <body> <DIV CLASS="navigation"> <div id='top-navigation-panel'> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td class='online-navigation'><a rel="prev" title="16.1.6.6 Tk Option Data" href="node643.html"><img src='../icons/previous.png' border='0' height='32' alt='Previous Page' width='32' /></A></td> <td class='online-navigation'><a rel="parent" title="16.1.6 Handy Reference" href="node637.html"><img src='../icons/up.png' border='0' height='32' alt='Up One Level' width='32' /></A></td> <td class='online-navigation'><a rel="next" title="16.1.6.8 The index Parameter" href="node645.html"><img src='../icons/next.png' border='0' height='32' alt='Next Page' width='32' /></A></td> <td align="center" width="100%">Python Library Reference</td> <td class='online-navigation'><a rel="contents" title="Table of Contents" href="contents.html"><img src='../icons/contents.png' border='0' height='32' alt='Contents' width='32' /></A></td> <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' border='0' height='32' alt='Module Index' width='32' /></a></td> <td class='online-navigation'><a rel="index" title="Index" href="genindex.html"><img src='../icons/index.png' border='0' height='32' alt='Index' width='32' /></A></td> </tr></table> <div class='online-navigation'> <b class="navlabel">Previous:</b> <a class="sectref" rel="prev" href="node643.html">16.1.6.6 Tk Option Data</A> <b class="navlabel">Up:</b> <a class="sectref" rel="parent" href="node637.html">16.1.6 Handy Reference</A> <b class="navlabel">Next:</b> <a class="sectref" rel="next" href="node645.html">16.1.6.8 The index Parameter</A> </div> <hr /></div> </DIV> <!--End of Navigation Panel--> <H3><A NAME="SECTION0018167000000000000000"> 16.1.6.7 Bindings and Events</A> </H3> <P> <a id='l2h-4552'><!--x--></a> <P> The bind method from the widget command allows you to watch for certain events and to have a callback function trigger when that event type occurs. The form of the bind method is: <P> <div class="verbatim"><pre> def bind(self, sequence, func, add=''): </pre></div> where: <P> <DL> <DT><STRONG>sequence</STRONG></DT> <DD>is a string that denotes the target kind of event. (See the bind man page and page 201 of John Ousterhout's book for details). <P> </DD> <DT><STRONG>func</STRONG></DT> <DD>is a Python function, taking one argument, to be invoked when the event occurs. An Event instance will be passed as the argument. (Functions deployed this way are commonly known as <var>callbacks</var>.) <P> </DD> <DT><STRONG>add</STRONG></DT> <DD>is optional, either "" or "<tt class="samp">+</tt>". Passing an empty string denotes that this binding is to replace any other bindings that this event is associated with. Preceeding with a "<tt class="samp">+</tt>" means that this function is to be added to the list of functions bound to this event type. </DD> </DL> <P> For example: <div class="verbatim"><pre> def turnRed(self, event): event.widget["activeforeground"] = "red" self.button.bind("<Enter>", self.turnRed) </pre></div> <P> Notice how the widget field of the event is being accesed in the <tt class="method">turnRed()</tt> callback. This field contains the widget that caught the X event. The following table lists the other event fields you can access, and how they are denoted in Tk, which can be useful when referring to the Tk man pages. <P> <div class="verbatim"><pre> Tk Tkinter Event Field Tk Tkinter Event Field -- ------------------- -- ------------------- %f focus %A char %h height %E send_event %k keycode %K keysym %s state %N keysym_num %t time %T type %w width %W widget %x x %X x_root %y y %Y y_root </pre></div> <P> <DIV CLASS="navigation"> <div class='online-navigation'><hr /> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td class='online-navigation'><a rel="prev" title="16.1.6.6 Tk Option Data" rel="prev" title="16.1.6.6 Tk Option Data" href="node643.html"><img src='../icons/previous.png' border='0' height='32' alt='Previous Page' width='32' /></A></td> <td class='online-navigation'><a rel="parent" title="16.1.6 Handy Reference" rel="parent" title="16.1.6 Handy Reference" href="node637.html"><img src='../icons/up.png' border='0' height='32' alt='Up One Level' width='32' /></A></td> <td class='online-navigation'><a rel="next" title="16.1.6.8 The index Parameter" rel="next" title="16.1.6.8 The index Parameter" href="node645.html"><img src='../icons/next.png' border='0' height='32' alt='Next Page' width='32' /></A></td> <td align="center" width="100%">Python Library Reference</td> <td class='online-navigation'><a rel="contents" title="Table of Contents" rel="contents" title="Table of Contents" href="contents.html"><img src='../icons/contents.png' border='0' height='32' alt='Contents' width='32' /></A></td> <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' border='0' height='32' alt='Module Index' width='32' /></a></td> <td class='online-navigation'><a rel="index" title="Index" rel="index" title="Index" href="genindex.html"><img src='../icons/index.png' border='0' height='32' alt='Index' width='32' /></A></td> </tr></table> <div class='online-navigation'> <b class="navlabel">Previous:</b> <a class="sectref" rel="prev" href="node643.html">16.1.6.6 Tk Option Data</A> <b class="navlabel">Up:</b> <a class="sectref" rel="parent" href="node637.html">16.1.6 Handy Reference</A> <b class="navlabel">Next:</b> <a class="sectref" rel="next" href="node645.html">16.1.6.8 The index Parameter</A> </div> </div> <hr /> <span class="release-info">Release 2.3.4, documentation updated on May 20, 2004.</span> </DIV> <!--End of Navigation Panel--> <ADDRESS> See <i><a href="about.html">About this document...</a></i> for information on suggesting changes. </ADDRESS> </BODY> </HTML>