Tkinter 8.4 reference - a GUI for Python (2009).pdf

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Tkinter 8.4 reference: a
GUI for Python
John W. Shipman
2009-07-14 11:41
Abstract
Describes the Tkinter widget set for constructing graphical user interfaces (GUIs) in the Python
programming language.
This publication is available in Web form 1 and also as a PDF document 2 . Please forward any
comments to tcc-doc@nmt.edu .
Table of Contents
1. What is Tkinter? ....................................................................................................................... 3
2. A minimal application .............................................................................................................. 3
3. Definitions .............................................................................................................................. 4
4. Layout management ................................................................................................................. 4
4.1. The .grid() method .................................................................................................... 5
4.2. Other grid management methods ................................................................................... 6
4.3. Configuring column and row sizes ................................................................................. 7
4.4. Making the root window resizeable ................................................................................ 7
5. Standard attributes ................................................................................................................... 8
5.1. Dimensions ................................................................................................................... 8
5.2. The coordinate system ................................................................................................... 9
5.3. Colors ........................................................................................................................... 9
5.4. Type fonts ..................................................................................................................... 9
5.5. Anchors ...................................................................................................................... 11
5.6. Relief styles ................................................................................................................. 11
5.7. Bitmaps ....................................................................................................................... 12
5.8. Cursors ....................................................................................................................... 12
5.9. Images ........................................................................................................................ 13
5.10. Geometry strings ........................................................................................................ 14
5.11. Window names ........................................................................................................... 15
5.12. Cap and join styles ..................................................................................................... 15
5.13. Dash patterns ............................................................................................................. 16
5.14. Matching stipple patterns ............................................................................................ 16
6. The Button widget ................................................................................................................ 17
7. The Canvas widget ................................................................................................................ 19
7.1. Canvas coordinates ...................................................................................................... 20
7.2. The Canvas display list ................................................................................................ 20
7.3. Canvas object IDs ........................................................................................................ 21
7.4. Canvas tags ................................................................................................................ 21
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7.5. Canvas tagOrId arguments ...................................................................................... 21
7.6. Methods on Canvas widgets ........................................................................................ 21
7.7. Canvas arc objects ....................................................................................................... 26
7.8. Canvas bitmap objects ................................................................................................. 28
7.9. Canvas image objects .................................................................................................. 28
7.10. Canvas line objects ..................................................................................................... 29
7.11. Canvas oval objects .................................................................................................... 30
7.12. Canvas polygon objects .............................................................................................. 32
7.13. Canvas rectangle objects ............................................................................................. 33
7.14. Canvas text objects ..................................................................................................... 35
7.15. Canvas window objects .............................................................................................. 36
8. The Checkbutton widget ...................................................................................................... 36
9. The Entry widget .................................................................................................................. 39
9.1. Scrolling an Entry widget ............................................................................................ 43
10. The Frame widget ................................................................................................................ 43
11. The Label widget ................................................................................................................ 44
12. The LabelFrame widget ...................................................................................................... 46
13. The Listbox widget ............................................................................................................ 47
13.1. Scrolling a Listbox widget ........................................................................................ 51
14. The Menu widget .................................................................................................................. 52
14.1. Menu item creation ( coption ) options ......................................................................... 55
15. The Menubutton widget ...................................................................................................... 56
16. The Message widget ............................................................................................................ 58
17. The OptionMenu widget ....................................................................................................... 59
18. The PanedWindow widget .................................................................................................... 60
18.1. PanedWindow child configuration options ................................................................... 62
19. The Radiobutton widget .................................................................................................... 63
20. The Scale widget ................................................................................................................ 66
21. The Scrollbar widget ........................................................................................................ 69
21.1. The Scrollbar command callback ............................................................................ 71
21.2. Connecting a Scrollbar to another widget ................................................................ 72
22. The Spinbox widget ............................................................................................................ 72
23. The Text widget .................................................................................................................. 77
23.1. Text widget indices ................................................................................................... 79
23.2. Text widget marks .................................................................................................... 80
23.3. Text widget images ................................................................................................... 81
23.4. Text widget windows ............................................................................................... 81
23.5. Text widget tags ....................................................................................................... 81
23.6. Setting tabs in a Text widget ...................................................................................... 82
23.7. The Text widget undo/redo stack .............................................................................. 82
23.8. Methods on Text widgets .......................................................................................... 83
24. Toplevel : Top-level window methods .................................................................................. 90
25. Universal widget methods ..................................................................................................... 92
26. Standardizing appearance ................................................................................................... 100
26.1. How to name a widget class ...................................................................................... 101
26.2. How to name a widget instance ................................................................................. 101
26.3. Resource specification lines ....................................................................................... 101
26.4. Rules for resource matching ...................................................................................... 102
27. Connecting your application logic to the widgets ................................................................... 103
28. Control variables: the values behind the widgets ................................................................... 103
29. Focus: routing keyboard input ............................................................................................. 105
30. Events ................................................................................................................................ 106
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30.1. Levels of binding ...................................................................................................... 107
30.2. Event sequences ....................................................................................................... 108
30.3. Event types .............................................................................................................. 108
30.4. Event modifiers ........................................................................................................ 109
30.5. Key names ............................................................................................................... 110
30.6. Writing your handler: The Event class ...................................................................... 112
30.7. The extra arguments trick .......................................................................................... 114
30.8. Virtual events ........................................................................................................... 115
31. Pop-up dialogs .................................................................................................................... 115
31.1. The tkMessageBox dialogs module .......................................................................... 115
31.2. The tkFileDialog module ..................................................................................... 117
31.3. The tkColorChooser module ................................................................................. 118
1. What is Tkinter?
Tkinter is a GUI (graphical user interface) widget set for Python. This document contains only the
commoner features.
This document applies to Python 2.5 and Tkinter 8.4 running in the X Window system under Linux.
Your version may vary.
Pertinent references:
An Introduction to Tkinter 3 by Fredrik Lundh.
Python and Tkinter Programming by John Grayson (Manning, 2000, ISBN 1-884777-81-3).
Python 2.5 quick reference 4 : general information about the Python language.
We'll start by looking at the visible part of Tkinter: creating the widgets and arranging them on the
screen. Later we will talk about how to connect the face—the “front panel”—of the application to the
logic behind it.
2. A minimal application
Here is a trivial Tkinter program containing only a Quit button:
#!/usr/local/bin/python
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from Tkinter import *
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class Application(Frame):
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def __init__(self, master=None):
Frame.__init__(self, master)
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self.grid()
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self.createWidgets()
def createWidgets(self):
self.quitButton = Button ( self, text='Quit',
command=self.quit )
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self.quitButton.grid()
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app = Application()
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app.master.title("Sample application")
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app.mainloop()
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1 This line makes the script self-executing, assuming that your system has the Python interpreter at
path /usr/local/bin/python .
2 This line imports the entire Tkinter package into your program's namespace.
3 Your application class must inherit from Tkinter's Frame class.
4 Calls the constructor for the parent class, Frame .
5 Necessary to make the application actually appear on the screen.
6 Creates a button labeled “Quit”.
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Places the button on the application.
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The main program starts here by instantiating the Application class.
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This method call sets the title of the window to “Sample application”.
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Starts the application's main loop, waiting for mouse and keyboard events.
3. Definitions
Before we proceed, let's define some of the common terms.
window
This term has different meanings in different contexts, but in general it refers to a rectangular area
somewhere on your display screen.
top-level window
A window that exists independently on your screen. It will be decorated with the standard frame
and controls for your system's desktop manager. You can move it around on your desktop. You
can generally resize it, although your application can prevent this
widget
The generic term for any of the building blocks that make up an application in a graphical user in-
terface. Examples of widgets: buttons, radiobuttons, text fields, frames, and text labels.
frame
In Tkinter, the Frame widget is the basic unit of organization for complex layouts. A frame is a
rectangular area that can contain other widgets.
child, parent
When any widget is created, a parent-child relationship is created. For example, if you place a text
label inside a frame, the frame is the parent of the label.
4. Layout management
Later we will discuss the widgets, the building blocks of your GUI application. How do widgets get
arranged in a window?
Although there are three different “geometry managers” in Tkinter, the author strongly prefers the
.grid() geometry manager for pretty much everything. This manager treats every window or frame
as a table—a gridwork of rows and columns.
•A cell is the area at the intersection of one row and one column.
•The width of each column is the width of the widest cell in that column.
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•The height of each row is the height of the largest cell in that row.
•For widgets that do not fill the entire cell, you can specify what happens to the extra space. You can
either leave the extra space outside the widget, or stretch the widget to fit it, in either the horizontal
or vertical dimension.
•You can combine multiple cells into one larger area, a process called spanning .
When you create a widget, it does not appear until you register it with a geometry manager. Hence,
construction and placing of a widget is a two-step process that goes something like this:
self. thing = Constructor ( parent , ...)
self. thing .grid(...)
where Constructor is one of the widget classes like Button , Frame , and so on, and parent is the
parent widget in which this child widget is being constructed. All widgets have a .grid() method
that you can use to tell the geometry manager where to put it.
4.1. The .grid() method
To display a widget w on your application screen:
w .grid( option = value , ...)
This method registers a widget w with the grid geometry manager—if you don't do this, the widget will
exist internally, but it will not be visible on the screen.
Here are the options to the .grid() geometry management method:
column
The column number where you want the widget gridded, counting from zero. The default
value is zero.
columnspan
Normally a widget occupies only one cell in the grid. However, you can grab multiple
cells of a row and merge them into one larger cell by setting the columnspan option to
the number of cells. For example, w .grid(row=0, column=2, columnspan=3)
would place widget w in a cell that spans columns 2, 3, and 4 of row 0.
To register w as a child of some widget w 2 , use in_= w 2 . The new parent w 2 must be a
descendant of the parent widget used when w was created.
in_
ipadx
Internal x padding. This dimension is added inside the widget inside its left and right
sides.
ipady
Internal y padding. This dimension is added inside the widget inside its top and bottom
borders.
padx
External x padding. This dimension is added to the left and right outside the widget.
pady
External y padding. This dimension is added above and below the widget.
row
The row number into which you want to insert the widget, counting from 0. The default
is the next higher-numbered unoccupied row.
rowspan
Normally a widget occupies only one cell in the grid. You can grab multiple adjacent
cells of a column, however, by setting the rowspan option to the number of cells to grab.
This option can be used in combination with the columnspan option to grab a block of
cells. For example, w .grid(row=3, column=2, rowspan=4, columnspan=5)
would place widget w in an area formed by merging 20 cells, with row numbers 3–6 and
column numbers 2–6.
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