{"id":1639,"date":"2020-12-11T10:19:21","date_gmt":"2020-12-11T10:19:21","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=1639"},"modified":"2025-04-03T06:09:42","modified_gmt":"2025-04-03T06:09:42","slug":"tkinter-event-binding","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/tkinter\/tkinter-event-binding\/","title":{"rendered":"Tkinter Event Binding"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the Tkinter event binding mechanism.<\/p>\n\n\n\n

Introduction to the Tkinter event binding #<\/a><\/h2>\n\n\n\n

Assigning a function<\/a> to an event of a widget is known as event binding<\/strong>. The assigned function will be invoked automatically when the event occurs.<\/p>\n\n\n\n

In the previous tutorial<\/a>, you learned how to bind a function to an event of a widget via the command<\/a><\/code> option. However, it’s important to note that not all Tkinter widgets<\/a> support the command<\/code> option.<\/p>\n\n\n\n

Therefore, Tkinter provides you with an alternative way for event binding via the bind()<\/code> method. <\/p>\n\n\n\n

The following shows the general syntax of the bind()<\/code> method:<\/p>\n\n\n

widget.bind(event, handler, add=None<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
When an event<\/code> occurs in the widget<\/code>, Tkinter will automatically invoke the handler<\/code> with the event details.<\/p>\n\n\n\n
If you want to register an additional handler, you can pass the '+'<\/code> to the add<\/code> argument. This allows you to have multiple event handlers responding to the same event.<\/p>\n\n\n\n
Tkinter event binding examples #<\/a><\/h2>\n\n\n\n
The following program illustrates how to bind the return_pressed<\/code> function to the Return<\/code> key pressed event of the 'Save'<\/code> button:<\/p>\n\n\n
import<\/span> tkinter as<\/span> tk\nfrom<\/span> tkinter import<\/span> ttk\n\n\ndef<\/span> return_pressed<\/span>(event)<\/span>:<\/span>\n    print('Return key pressed.'<\/span>)\n\n\nroot = tk.Tk()\n\nbtn = ttk.Button(root, text='Save'<\/span>)\nbtn.bind('<Return>'<\/span>, return_pressed)\n\n\nbtn.focus()\nbtn.pack(expand=True<\/span>)\n\nroot.mainloop()<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the following statement calls the bind()<\/code> method on the button widget to bind the Return<\/code> key pressed event:<\/p>\n\n\n
btn.bind('<Return>'<\/span>, return_pressed)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example illustrates how to use the bind()<\/code> method to register multiple handlers for the same event:<\/p>\n\n\n
import<\/span> tkinter as<\/span> tk\nfrom<\/span> tkinter import<\/span> ttk\n\n\ndef<\/span> return_pressed<\/span>(event)<\/span>:<\/span>\n    print('Return key pressed.'<\/span>)\n\n\ndef<\/span> log<\/span>(event)<\/span>:<\/span>\n    print(event)\n\n\nroot = tk.Tk()\n\nbtn = ttk.Button(root, text='Save'<\/span>)\nbtn.bind('<Return>'<\/span>, return_pressed)\nbtn.bind('<Return>'<\/span>, log, add='+'<\/span>)\n\n\nbtn.focus()\nbtn.pack(expand=True<\/span>)\n\nroot.mainloop()<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
When you move the focus to the button and press the Return<\/code> key, Tkinter automatically invokes the return_pressed<\/code> and log<\/code> functions.<\/p>\n\n\n\n
The following binds the log()<\/code> function to the Return<\/code> key pressed event of the 'Save'<\/code> button:<\/p>\n\n\n
btn.bind('<Return>'<\/span>, log, add='+'<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this statement, the third argument add='+'<\/code> registered additional handler, which is the log()<\/code> function. <\/p>\n\n\n\n
If you don’t specify the add='+'<\/code> argument, the bind()<\/code> method will replace the existing handler (return_pressed<\/code>) by the new one (log<\/code>).<\/p>\n\n\n\n
Event patterns #<\/a><\/h2>\n\n\n\n
Tkinter uses event patterns to map event names with handlers. For example, the <Return><\/code> denotes the Return key pressed.<\/p>\n\n\n\n
The following shows the general syntax of an event pattern:<\/p>\n\n\n
<modifier-type-detail><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, an event is surrounded by angle brackets (<><\/code>). Inside the angle brackets, there are zero or more modifiers, an event type, and detailed information about the event. <\/p>\n\n\n\n
For example, the <KeyPress-A><\/code> denotes a keyboard press of the key A<\/code> . and <Alt-Control-KeyPress-KP_Delete><\/code> represents a keypress of Alt + Ctrl + Delete<\/code>.<\/p>\n\n\n\n
The following section shows the most commonly used event modifiers, event types, and event details.<\/p>\n\n\n\n
Event modifiers #<\/a><\/h3>\n\n\n\n
The following table lists the most commonly used event modifiers:<\/p>\n\n\n\n
Event Modifier<\/th>Meaning<\/th><\/tr><\/thead>
Alt<\/td>The Alt key is held<\/td><\/tr>
Control<\/td>The Ctrl key is held<\/td><\/tr>
Shift<\/td>The Shift key is held<\/td><\/tr>
Any<\/td>This modifier makes an event type general. For example, the event pattern <Any-KeyPress><\/code> applies to the keypress of any key.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Event types #<\/a><\/h3>\n\n\n\n
The following table shows the most commonly used event types:<\/p>\n\n\n\n
Type<\/th>Name<\/th>Description<\/th><\/tr><\/thead>
36<\/td>Activate<\/code><\/td>The state option of a widget changes from inactive to active.<\/td><\/tr>
4<\/td>Button<\/code><\/td>One mouse button is pressed<\/td><\/tr>
5<\/td>ButtonRelease<\/code><\/td>One mouse button is released<\/td><\/tr>
22<\/td>Configure<\/code><\/td>The size of the widget is changed<\/td><\/tr>
37<\/td>Deactivate<\/code><\/td>The state option of a widget changes from active to inactive.<\/td><\/tr>
17<\/td>Destroy<\/code><\/td>A widget is being destroyed.<\/td><\/tr>
7<\/td>Enter<\/code><\/td>The mouse pointer is moved into a visible part of a widget.<\/td><\/tr>
12<\/td>Expose<\/code><\/td>Some part of the widget or application is visible after having been covered up by another window.<\/td><\/tr>
9<\/td>FocusIn<\/code><\/td>The input focus was moved into a widget.<\/td><\/tr>
10<\/td>FocusOut<\/code><\/td>The input focus was moved out of a widget.<\/td><\/tr>
2<\/td>KeyPress<\/code><\/td>A key is pressed.<\/td><\/tr>
3<\/td>KeyRelease<\/code><\/td>A key is released<\/td><\/tr>
8<\/td>Leave<\/code><\/td>The mouse pointer is moved out of a widget.<\/td><\/tr>
19<\/td>Map<\/code><\/td>A widget is being placed on a container e.g., calling the pack() or grid() method.<\/td><\/tr>
6<\/td>Motion<\/code><\/td>The mouse pointer is moved entirely within a widget.<\/td><\/tr>
38<\/td>MouseWheel<\/code><\/td>The user moved the mouse wheel up or down.<\/td><\/tr>
18<\/td>Unmap<\/code><\/td>A widget is being unmapped and is no longer visible, for example when calling the grid_remove()<\/code> method on the widget.<\/td><\/tr>
15<\/td>Visibility<\/code><\/td>At least some part of the application window becomes visible on the screen.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Event Detail #<\/a><\/h3>\n\n\n\n
The following table shows several ways to name keys:<\/p>\n\n\n\n
.keysym<\/code><\/th>.keycode<\/code><\/th>.keysym_num<\/code><\/th>Key<\/th><\/tr><\/thead>
Alt_L<\/code><\/td>64<\/code><\/td>65513<\/code><\/td>The left-hand alt key<\/td><\/tr>
Alt_R<\/code><\/td>113<\/code><\/td>65514<\/code><\/td>The right-hand alt key<\/td><\/tr>
BackSpace<\/code><\/td>22<\/code><\/td>65288<\/code><\/td>backspace<\/td><\/tr>
Cancel<\/code><\/td>110<\/code><\/td>65387<\/code><\/td>break<\/td><\/tr>
Caps_Lock<\/code><\/td>66<\/code><\/td>65549<\/code><\/td>CapsLock<\/td><\/tr>
Control_L<\/code><\/td>37<\/code><\/td>65507<\/code><\/td>The left-hand control key<\/td><\/tr>
Control_R<\/code><\/td>109<\/code><\/td>65508<\/code><\/td>The right-hand control key<\/td><\/tr>
Delete<\/code><\/td>107<\/code><\/td>65535<\/code><\/td>Delete<\/td><\/tr>
Down<\/code><\/td>104<\/code><\/td>65364<\/code><\/td>\u2193<\/td><\/tr>
End<\/code><\/td>103<\/code><\/td>65367<\/code><\/td>end<\/td><\/tr>
Escape<\/code><\/td>9<\/code><\/td>65307<\/code><\/td>esc<\/td><\/tr>
Execute<\/code><\/td>111<\/code><\/td>65378<\/code><\/td>SysReq<\/td><\/tr>
F1<\/code><\/td>67<\/code><\/td>65470<\/code><\/td>Function key F1<\/td><\/tr>
F2<\/code><\/td>68<\/code><\/td>65471<\/code><\/td>Function key F2<\/td><\/tr>
Fi<\/sub><\/code><\/td>66+i<\/code><\/td>65469+i<\/code><\/td>Function key Fi<\/sub><\/td><\/tr>
F12<\/code><\/td>96<\/code><\/td>65481<\/code><\/td>Function key F12<\/td><\/tr>
Home<\/code><\/td>97<\/code><\/td>65360<\/code><\/td>home<\/td><\/tr>
Insert<\/code><\/td>106<\/code><\/td>65379<\/code><\/td>insert<\/td><\/tr>
Left<\/code><\/td>100<\/code><\/td>65361<\/code><\/td>\u2190<\/td><\/tr>
Linefeed<\/code><\/td>54<\/code><\/td>106<\/code><\/td>Linefeed (control-J)<\/td><\/tr>
KP_0<\/code><\/td>90<\/code><\/td>65438<\/code><\/td>0 on the keypad<\/td><\/tr>
KP_1<\/code><\/td>87<\/code><\/td>65436<\/code><\/td>1 on the keypad<\/td><\/tr>
KP_2<\/code><\/td>88<\/code><\/td>65433<\/code><\/td>2 on the keypad<\/td><\/tr>
KP_3<\/code><\/td>89<\/code><\/td>65435<\/code><\/td>3 on the keypad<\/td><\/tr>
KP_4<\/code><\/td>83<\/code><\/td>65430<\/code><\/td>4 on the keypad<\/td><\/tr>
KP_5<\/code><\/td>84<\/code><\/td>65437<\/code><\/td>5 on the keypad<\/td><\/tr>
KP_6<\/code><\/td>85<\/code><\/td>65432<\/code><\/td>6 on the keypad<\/td><\/tr>
KP_7<\/code><\/td>79<\/code><\/td>65429<\/code><\/td>7 on the keypad<\/td><\/tr>
KP_8<\/code><\/td>80<\/code><\/td>65431<\/code><\/td>8 on the keypad<\/td><\/tr>
KP_9<\/code><\/td>81<\/code><\/td>65434<\/code><\/td>9 on the keypad<\/td><\/tr>
KP_Add<\/code><\/td>86<\/code><\/td>65451<\/code><\/td>+ on the keypad<\/td><\/tr>
KP_Begin<\/code><\/td>84<\/code><\/td>65437<\/code><\/td>The center key (same key as 5) on the keypad<\/td><\/tr>
KP_Decimal<\/code><\/td>91<\/code><\/td>65439<\/code><\/td>Decimal (.<\/code>) on the keypad<\/td><\/tr>
KP_Delete<\/code><\/td>91<\/code><\/td>65439<\/code><\/td>delete on the keypad<\/td><\/tr>
KP_Divide<\/code><\/td>112<\/code><\/td>65455<\/code><\/td>\/<\/code> on the keypad<\/td><\/tr>
KP_Down<\/code><\/td>88<\/code><\/td>65433<\/code><\/td>\u2193 on the keypad<\/td><\/tr>
KP_End<\/code><\/td>87<\/code><\/td>65436<\/code><\/td>end on the keypad<\/td><\/tr>
KP_Enter<\/code><\/td>108<\/code><\/td>65421<\/code><\/td>enter on the keypad<\/td><\/tr>
KP_Home<\/code><\/td>79<\/code><\/td>65429<\/code><\/td>home on the keypad<\/td><\/tr>
KP_Insert<\/code><\/td>90<\/code><\/td>65438<\/code><\/td>insert on the keypad<\/td><\/tr>
KP_Left<\/code><\/td>83<\/code><\/td>65430<\/code><\/td>\u2190 on the keypad<\/td><\/tr>
KP_Multiply<\/code><\/td>63<\/code><\/td>65450<\/code><\/td>\u00d7 on the keypad<\/td><\/tr>
KP_Next<\/code><\/td>89<\/code><\/td>65435<\/code><\/td>PageDown on the keypad<\/td><\/tr>
KP_Prior<\/code><\/td>81<\/code><\/td>65434<\/code><\/td>PageUp on the keypad<\/td><\/tr>
KP_Right<\/code><\/td>85<\/code><\/td>65432<\/code><\/td>\u2192 on the keypad<\/td><\/tr>
KP_Subtract<\/code><\/td>82<\/code><\/td>65453<\/code><\/td>-<\/code> on the keypad<\/td><\/tr>
KP_Up<\/code><\/td>80<\/code><\/td>65431<\/code><\/td>\u2191 on the keypad<\/td><\/tr>
Next<\/code><\/td>105<\/code><\/td>65366<\/code><\/td>PageDown<\/td><\/tr>
Num_Lock<\/code><\/td>77<\/code><\/td>65407<\/code><\/td>NumLock<\/td><\/tr>
Pause<\/code><\/td>110<\/code><\/td>65299<\/code><\/td>pause<\/td><\/tr>
Print<\/code><\/td>111<\/code><\/td>65377<\/code><\/td>PrintScrn<\/td><\/tr>
Prior<\/code><\/td>99<\/code><\/td>65365<\/code><\/td>PageUp<\/td><\/tr>
Return<\/code><\/td>36<\/code><\/td>65293<\/code><\/td>Enter key<\/td><\/tr>
Right<\/code><\/td>102<\/code><\/td>65363<\/code><\/td>\u2192<\/td><\/tr>
Scroll_Lock<\/code><\/td>78<\/code><\/td>65300<\/code><\/td>ScrollLock<\/td><\/tr>
Shift_L<\/code><\/td>50<\/code><\/td>65505<\/code><\/td>The left-hand shift key<\/td><\/tr>
Shift_R<\/code><\/td>62<\/code><\/td>65506<\/code><\/td>The right-hand shift key<\/td><\/tr>
Tab<\/code><\/td>23<\/code><\/td>65289<\/code><\/td>The tab key<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Binding events to root window #<\/a><\/h2>\n\n\n\n
So far, you have learned how to bind an event to a particular widget. Tkinter also allows you to bind an event to the top-level window. <\/p>\n\n\n\n
In this case, the syntax for the bind()<\/code> is the same except that you can call it on the root window like this:<\/p>\n\n\n
root.bind('<Return>'<\/span>, handler)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The levels of binding #<\/a><\/h2>\n\n\n\n
In the previous example, you have learned how to bind an event to a particular instance of a widget. This is an instance-level binding<\/strong>.<\/p>\n\n\n\n
Tkinter also allows you to bind an event to all the instances of a widget. For example, you can bind the event to all the Entry<\/code> widgets in a program:<\/p>\n\n\n
root.bind_class('Entry'<\/span>, '<Control-V>'<\/span>, paste)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
This is a class-level binding<\/strong> because you bind the event to a class instead of an instance.<\/p>\n\n\n\n
Unbinding events #<\/a><\/h2>\n\n\n\n
Sometimes, you may want to undo the effect of an earlier binding. To do it, you can use the unbind()<\/code> method:<\/p>\n\n\n
widget.unbind(event)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example unbinds the event from the btn<\/code> button:<\/p>\n\n\n
btn.unbind('<Return>'<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
    \n
  • Use the bind()<\/code> method to bind an event to a widget.<\/li>\n\n\n\n
  • Tkinter supports both instance-level and class-level bindings.<\/li>\n<\/ul>\n
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    Was this tutorial helpful ?<\/div>\n\t\t
    \n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t
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By the way, you use the Entry<\/a><\/code> widget to create a textbox in Tkinter.<\/p>\n\n\n\n