[Python编程(第4版)].(Programming.Python.4th.Edition).Mark.Lutz.文字版

Both kinds of buttons provide both command a n d variable o p t i o n s. T h e command option

lets you register a callback to be run immediately on button-press events, much like

normal Button widgets. But by associating a tkinter variable with the variable option,

you can also fetch or change widget state at any time by fetching or changing the value

of the widget’s associated variable.

Since it’s a bit simpler, let’s start with the tkinter Checkbutton. Example 8-22 creates

the set of five captured in Figure 8-26. To make this more useful, it also adds a button

that dumps the current state of all Checkbuttons and attaches an instance of the verifying

Quitter button we built earlier in the tour.

Figure 8-26. demoCheck in action

Example 8-22. PP4E\Gui\Tour\demoCheck.py

"create a bar of check buttons that run dialog demos"

from tkinter import * # get base widget set

from dialogTable import demos # get canned dialogs

from quitter import Quitter # attach a quitter object to "me"

class Demo(Frame):

def __init__(self, parent=None, **options):

Frame.__init__(self, parent, **options)

self.pack()

self.tools()

Label(self, text="Check demos").pack()

self.vars = []

for key in demos:

var = IntVar()

Checkbutton(self,

text=key,

variable=var,

command=demos[key]).pack(side=LEFT)

self.vars.append(var)

def report(self):

for var in self.vars:

print(var.get(), end=' ') # current toggle settings: 1 or 0

print()

def tools(self):

frm = Frame(self)

frm.pack(side=RIGHT)

458 | Chapter 8: A tkinter Tour, Part 1

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