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

demo objects was something more useful, like a text editor, calculator, or clock, you’ll
better appreciate the point of this example.

Besides demo object frames, this composite window also contains no fewer than five
instances of the Quitter button we wrote earlier (all of which verify the request and any
one of which can end the GUI) and a States button to dump the current values of all
the embedded demo objects at once (it calls each object’s report method, if it has one).
Here is a sample of the sort of output that shows up in the stdout stream after interacting
with widgets on this display; States output is in bold:

C:\...\PP4E\Gui\Tour> python demoAll_frm.py

in onMove 0

in onMove 0

demoDlg: none

demoCheck: 0 0 0 0 0

demoRadio: Error

demoScale: 0

you pressed Input

result: 1.234

in onMove 1

demoDlg: none

demoCheck: 1 0 1 1 0

demoRadio: Input

demoScale: 1

you pressed Query

result: yes

in onMove 2

You picked 2

None

in onMove 3

You picked 3

C:/Users/mark/Stuff/Books/4E/PP4E/dev/Examples/PP4E/Launcher.py

3

Query

1 1 1 1 0

demoDlg: none

demoCheck: 1 1 1 1 0

demoRadio: Query

demoScale: 3

Importing by name string

The only substantially tricky part of this script is its use of Python’s built-in
import function to import a module by a name string. Look at the following two
lines from the script’s addComponents function:

module = __import__(demo) # import module by name string

part = module.Demo(root) # attach an instance of its Demo

This is equivalent to saying something like this:

import 'demoDlg'

part = 'demoDlg'.Demo(root)

Running GUI Code Three Ways | 473