On to the code; let’s start out by quickly stepping through a few small examples that illustrate basic concepts and show the windows they create on the computer display. The examples will become progressively more sophisticated as we move along, but let’s get a handle on the fundamentals first.
The usual first example for GUI systems is to show how to display a “Hello World” message in a window. As coded in Example 7-1, it’s just four lines in Python.
Example 7-1. PP4E\Gui\Intro\gui1.py
from tkinter import Label # get a widget object widget = Label(None, text='Hello GUI world!') # make one widget.pack() # arrange it widget.mainloop() # start event loop
This is a complete Python tkinter GUI program. When this script is run, we get a simple window with a label in the middle; it looks like Figure 7-1 on my Windows 7 laptop (I stretched some windows in this book horizontally to reveal their window titles; your platform’s window system may vary).
Figure 7-1. “Hello World” (gui1) on Windows
This isn’t much to write home about yet, but notice that this is a completely functional, independent window on the computer’s display. It can be maximized to take up the entire screen, minimized to hide it in the system bar, and resized. Click on the window’s “X” box in the top right to kill the window and exit the program.
The script that ...