projects / OpenSPARC-T2-SAM / blame
| Commit | Line | Data |
|---|---|---|
| 920dae64 AT |
1 | <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
| 2 | <html> | |
| 3 | <head> | |
| 4 | <link rel="STYLESHEET" href="lib.css" type='text/css' /> | |
| 5 | <link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" /> | |
| 6 | <link rel='start' href='../index.html' title='Python Documentation Index' /> | |
| 7 | <link rel="first" href="lib.html" title='Python Library Reference' /> | |
| 8 | <link rel='contents' href='contents.html' title="Contents" /> | |
| 9 | <link rel='index' href='genindex.html' title='Index' /> | |
| 10 | <link rel='last' href='about.html' title='About this document...' /> | |
| 11 | <link rel='help' href='about.html' title='About this document...' /> | |
| 12 | <link rel="next" href="node727.html" /> | |
| 13 | <link rel="prev" href="node725.html" /> | |
| 14 | <link rel="parent" href="node722.html" /> | |
| 15 | <link rel="next" href="node727.html" /> | |
| 16 | <meta name='aesop' content='information' /> | |
| 17 | <title>16.1.6.4 Coupling Widget Variables</title> | |
| 18 | </head> | |
| 19 | <body> | |
| 20 | <DIV CLASS="navigation"> | |
| 21 | <div id='top-navigation-panel' xml:id='top-navigation-panel'> | |
| 22 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> | |
| 23 | <tr> | |
| 24 | <td class='online-navigation'><a rel="prev" title="16.1.6.3 Packer Options" | |
| 25 | href="node725.html"><img src='../icons/previous.png' | |
| 26 | border='0' height='32' alt='Previous Page' width='32' /></A></td> | |
| 27 | <td class='online-navigation'><a rel="parent" title="16.1.6 Handy Reference" | |
| 28 | href="node722.html"><img src='../icons/up.png' | |
| 29 | border='0' height='32' alt='Up One Level' width='32' /></A></td> | |
| 30 | <td class='online-navigation'><a rel="next" title="16.1.6.5 The Window Manager" | |
| 31 | href="node727.html"><img src='../icons/next.png' | |
| 32 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
| 33 | <td align="center" width="100%">Python Library Reference</td> | |
| 34 | <td class='online-navigation'><a rel="contents" title="Table of Contents" | |
| 35 | href="contents.html"><img src='../icons/contents.png' | |
| 36 | border='0' height='32' alt='Contents' width='32' /></A></td> | |
| 37 | <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' | |
| 38 | border='0' height='32' alt='Module Index' width='32' /></a></td> | |
| 39 | <td class='online-navigation'><a rel="index" title="Index" | |
| 40 | href="genindex.html"><img src='../icons/index.png' | |
| 41 | border='0' height='32' alt='Index' width='32' /></A></td> | |
| 42 | </tr></table> | |
| 43 | <div class='online-navigation'> | |
| 44 | <b class="navlabel">Previous:</b> | |
| 45 | <a class="sectref" rel="prev" href="node725.html">16.1.6.3 Packer Options</A> | |
| 46 | <b class="navlabel">Up:</b> | |
| 47 | <a class="sectref" rel="parent" href="node722.html">16.1.6 Handy Reference</A> | |
| 48 | <b class="navlabel">Next:</b> | |
| 49 | <a class="sectref" rel="next" href="node727.html">16.1.6.5 The Window Manager</A> | |
| 50 | </div> | |
| 51 | <hr /></div> | |
| 52 | </DIV> | |
| 53 | <!--End of Navigation Panel--> | |
| 54 | ||
| 55 | <H3><A NAME="SECTION0018164000000000000000"> | |
| 56 | 16.1.6.4 Coupling Widget Variables</A> | |
| 57 | </H3> | |
| 58 | <P> | |
| 59 | The current-value setting of some widgets (like text entry widgets) | |
| 60 | can be connected directly to application variables by using special | |
| 61 | options. These options are <code>variable</code>, <code>textvariable</code>, | |
| 62 | <code>onvalue</code>, <code>offvalue</code>, and <code>value</code>. This | |
| 63 | connection works both ways: if the variable changes for any reason, | |
| 64 | the widget it's connected to will be updated to reflect the new value. | |
| 65 | ||
| 66 | <P> | |
| 67 | Unfortunately, in the current implementation of <tt class="module"><a href="module-Tkinter.html">Tkinter</a></tt> it is | |
| 68 | not possible to hand over an arbitrary Python variable to a widget | |
| 69 | through a <code>variable</code> or <code>textvariable</code> option. The only | |
| 70 | kinds of variables for which this works are variables that are | |
| 71 | subclassed from a class called Variable, defined in the | |
| 72 | <tt class="module"><a href="module-Tkinter.html">Tkinter</a></tt> module. | |
| 73 | ||
| 74 | <P> | |
| 75 | There are many useful subclasses of Variable already defined: | |
| 76 | <tt class="class">StringVar</tt>, <tt class="class">IntVar</tt>, <tt class="class">DoubleVar</tt>, and | |
| 77 | <tt class="class">BooleanVar</tt>. To read the current value of such a variable, | |
| 78 | call the <tt class="method">get()</tt> method on | |
| 79 | it, and to change its value you call the <tt class="method">set()</tt> method. If | |
| 80 | you follow this protocol, the widget will always track the value of | |
| 81 | the variable, with no further intervention on your part. | |
| 82 | ||
| 83 | <P> | |
| 84 | For example: | |
| 85 | <div class="verbatim"><pre> | |
| 86 | class App(Frame): | |
| 87 | def __init__(self, master=None): | |
| 88 | Frame.__init__(self, master) | |
| 89 | self.pack() | |
| 90 | ||
| 91 | self.entrythingy = Entry() | |
| 92 | self.entrythingy.pack() | |
| 93 | ||
| 94 | # here is the application variable | |
| 95 | self.contents = StringVar() | |
| 96 | # set it to some value | |
| 97 | self.contents.set("this is a variable") | |
| 98 | # tell the entry widget to watch this variable | |
| 99 | self.entrythingy["textvariable"] = self.contents | |
| 100 | ||
| 101 | # and here we get a callback when the user hits return. | |
| 102 | # we will have the program print out the value of the | |
| 103 | # application variable when the user hits return | |
| 104 | self.entrythingy.bind('<Key-Return>', | |
| 105 | self.print_contents) | |
| 106 | ||
| 107 | def print_contents(self, event): | |
| 108 | print "hi. contents of entry is now ---->", \ | |
| 109 | self.contents.get() | |
| 110 | </pre></div> | |
| 111 | ||
| 112 | <P> | |
| 113 | ||
| 114 | <DIV CLASS="navigation"> | |
| 115 | <div class='online-navigation'> | |
| 116 | <p></p><hr /> | |
| 117 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> | |
| 118 | <tr> | |
| 119 | <td class='online-navigation'><a rel="prev" title="16.1.6.3 Packer Options" | |
| 120 | href="node725.html"><img src='../icons/previous.png' | |
| 121 | border='0' height='32' alt='Previous Page' width='32' /></A></td> | |
| 122 | <td class='online-navigation'><a rel="parent" title="16.1.6 Handy Reference" | |
| 123 | href="node722.html"><img src='../icons/up.png' | |
| 124 | border='0' height='32' alt='Up One Level' width='32' /></A></td> | |
| 125 | <td class='online-navigation'><a rel="next" title="16.1.6.5 The Window Manager" | |
| 126 | href="node727.html"><img src='../icons/next.png' | |
| 127 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
| 128 | <td align="center" width="100%">Python Library Reference</td> | |
| 129 | <td class='online-navigation'><a rel="contents" title="Table of Contents" | |
| 130 | href="contents.html"><img src='../icons/contents.png' | |
| 131 | border='0' height='32' alt='Contents' width='32' /></A></td> | |
| 132 | <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' | |
| 133 | border='0' height='32' alt='Module Index' width='32' /></a></td> | |
| 134 | <td class='online-navigation'><a rel="index" title="Index" | |
| 135 | href="genindex.html"><img src='../icons/index.png' | |
| 136 | border='0' height='32' alt='Index' width='32' /></A></td> | |
| 137 | </tr></table> | |
| 138 | <div class='online-navigation'> | |
| 139 | <b class="navlabel">Previous:</b> | |
| 140 | <a class="sectref" rel="prev" href="node725.html">16.1.6.3 Packer Options</A> | |
| 141 | <b class="navlabel">Up:</b> | |
| 142 | <a class="sectref" rel="parent" href="node722.html">16.1.6 Handy Reference</A> | |
| 143 | <b class="navlabel">Next:</b> | |
| 144 | <a class="sectref" rel="next" href="node727.html">16.1.6.5 The Window Manager</A> | |
| 145 | </div> | |
| 146 | </div> | |
| 147 | <hr /> | |
| 148 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
| 149 | </DIV> | |
| 150 | <!--End of Navigation Panel--> | |
| 151 | <ADDRESS> | |
| 152 | See <i><a href="about.html">About this document...</a></i> for information on suggesting changes. | |
| 153 | </ADDRESS> | |
| 154 | </BODY> | |
| 155 | </HTML> |