Page 72 - Programming the Raspberry Pi Getting Started with Python

For the sake of efficiency, it is better if we create a single “converter” during __init__ and just use
the same one every time the button is clicked. Therefore, we create a variable called self.t_conv to
reference the convertor. The convert method then just becomes this:

Here is the full listing of the program:

Other GUI Widgets
In the temperature converter, we just used text fields (class Entry) and labels (class Label). As you
would expect, you can build lots of other user interface controls into your application. Figure 7-5
shows the main screen of a “kitchen sink” application that illustrates most of the controls you can use
in Tkinter. This program is available as 07_05_kitchen_sink.py.

Figure 7-5 A “kitchen sink” application
Checkbutton
The Checkbox widget (first column, second row of Figure 7-5) is created like this:

This line of code just creates a Checkbutton with a label next to it. If we have gone to the effort of
placing a check box on the window, we’ll also want a way of finding out whether or not it is checked.