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20. The Radiobutton widget

Radiobuttons are sets of related widgets that allow the user to select only one of a set of choices. Each radiobutton consists of two parts, the indicator and the label:

To create a new radiobutton widget as the child of a root window or frame named parent:

    w = tk.Radiobutton(parent, option, ...)

This constructor returns the new Radiobutton widget. Options:

Table 29. Radiobutton widget options

activebackground The background color when the mouse is over the radiobutton. See Section 5.3, “Colors”.
activeforeground The foreground color when the mouse is over the radiobutton.
anchor If the widget inhabits a space larger than it needs, this option specifies where the radiobutton will sit in that space. The default is anchor=tk.CENTER. For other positioning options, see Section 5.5, “Anchors”. For example, if you set anchor=tk.NE, the radiobutton will be placed in the top right corner of the available space.
bg or background The normal background color behind the indicator and label.
bitmap To display a monochrome image on a radiobutton, set this option to a bitmap; see Section 5.7, “Bitmaps”.
bd or borderwidth The size of the border around the indicator part itself. Default is two pixels. For possible values, see Section 5.1, “Dimensions”.
command A procedure to be called every time the user changes the state of this radiobutton.
compound If you specify both text and a graphic (either a bitmap or an image), this option specifies where the graphic appears relative to the text. Possible values are tk.NONE (the default value), tk.TOP, tk.BOTTOM, tk.LEFT, tk.RIGHT, and tk.CENTER. For example, compound=tk.BOTTOM would position the graphic below the text. If you specify compound=tk.NONE, the graphic is displayed but the text (if any) is not.
cursor If you set this option to a cursor name (see Section 5.8, “Cursors”), the mouse cursor will change to that pattern when it is over the radiobutton.
disabledforeground The foreground color used to render the text of a disabled radiobutton. The default is a stippled version of the default foreground color.
font The font used for the text. See Section 5.4, “Type fonts”.
fg or foreground The color used to render the text.
height The number of lines (not pixels) of text on the radiobutton. Default is 1.
highlightbackground The color of the focus highlight when the radiobutton does not have focus. See Section 53, “Focus: routing keyboard input”.
highlightcolor The color of the focus highlight when the radiobutton has the focus.
highlightthickness The thickness of the focus highlight. Default is 1. Set highlightthickness=0 to suppress display of the focus highlight.
image To display a graphic image instead of text for this radiobutton, set this option to an image object. See Section 5.9, “Images”. The image appears when the radiobutton is not selected; compare selectimage, below.
indicatoron Normally a radiobutton displays its indicator. If you set this option to zero, the indicator disappears, and the entire widget becomes a “push-push” button that looks raised when it is cleared and sunken when it is set. You may want to increase the borderwidth value to make it easier to see the state of such a control.
justify If the text contains multiple lines, this option controls how the text is justified: tk.CENTER (the default), tk.LEFT, or tk.RIGHT.
offrelief If you suppress the indicator by asserting indicatoron=False, the offrelief option specifies the relief style to be displayed when the radiobutton is not selected. The default values is tk.RAISED.
overrelief Specifies the relief style to be displayed when the mouse is over the radiobutton.
padx How much space to leave to the left and right of the radiobutton and text. Default is 1.
pady How much space to leave above and below the radiobutton and text. Default is 1.
relief By default, a radiobutton will have tk.FLAT relief, so it doesn't stand out from its background. See Section 5.6, “Relief styles” for more 3-d effect options. You can also use relief=tk.SOLID, which displays a solid black frame around the radiobutton.
selectcolor The color of the radiobutton when it is set. Default is red.
selectimage If you are using the image option to display a graphic instead of text when the radiobutton is cleared, you can set the selectimage option to a different image that will be displayed when the radiobutton is set. See Section 5.9, “Images”.
state The default is state=tk.NORMAL, but you can set state=tk.DISABLED to gray out the control and make it unresponsive. If the cursor is currently over the radiobutton, the state is tk.ACTIVE.
takefocus By default, the input focus (see Section 53, “Focus: routing keyboard input”) will pass through a radiobutton. If you set takefocus=0, focus will not visit this radiobutton.
text The label displayed next to the radiobutton. Use newlines ('\n') to display multiple lines of text.
textvariable If you need to change the label on a radiobutton during execution, create a StringVar (see Section 52, “Control variables: the values behind the widgets”) to manage the current value, and set this option to that control variable. Whenever the control variable's value changes, the radiobutton's annotation will automatically change to that text as well.
underline With the default value of -1, none of the characters of the text label are underlined. Set this option to the index of a character in the text (counting from zero) to underline that character.
value When a radiobutton is turned on by the user, its control variable is set to its current value option. If the control variable is an IntVar, give each radiobutton in the group a different integer value option. If the control variable is a StringVar, give each radiobutton a different string value option.
variable The control variable that this radiobutton shares with the other radiobuttons in the group; see Section 52, “Control variables: the values behind the widgets”. This can be either an IntVar or a StringVar.
width The default width of a radiobutton is determined by the size of the displayed image or text. You can set this option to a number of characters (not pixels) and the radiobutton will always have room for that many characters.
wraplength Normally, lines are not wrapped. You can set this option to a number of characters and all lines will be broken into pieces no longer than that number.

Methods on radiobutton objects include:

.deselect()

Clears (turns off) the radiobutton.

.flash()

Flashes the radiobutton a few times between its active and normal colors, but leaves it the way it started.

.invoke()

You can call this method to get the same actions that would occur if the user clicked on the radiobutton to change its state.

.select()

Sets (turns on) the radiobutton.