CSC111 Lab 14 2015

--D. Thiebaut (talk) 13:26, 29 April 2015 (EDT)

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TK Lab

This lab covers TKinter on Python 3.X. A very good tutorial on TK can be found on Lynda.com.

TK Skeleton

• Create a new program called tkSkel0.py with the code below. You should work in Idle, as this will automatically make tkinter and ttk findable for Python.

from tkinter import *
from tkinter import ttk

 
    
def main():
    global label
    rootWindow = Tk()

    label = ttk.Label( rootWindow, text="Hello World!" )
    label.pack()

    rootWindow.mainloop()

main()

• Run the program. Be careful, as this will create a tiny window on your screen, which may not be easily visible. But it should be there!
• Congratulations. This is the "Hello World!" version of Python using the TKinter graphics environment.

Adding a Button

• Now try adding some more code to your application:

from tkinter import *
from tkinter import ttk
    
def main():
    rootWindow = Tk()

    label = ttk.Label( rootWindow, text="Hello World!" )
    label.pack()

    button1 = ttk.Button( rootWindow, text="Change Label" )
    button1.pack()
    
    rootWindow.mainloop()

main()

• Run the code. Observe that a new button will have appeared. Click on the button a few times. Why is it not doing anything?
• If your answer is that we haven't define an action for the button, you are absolutely right!
• Let's add a new function to the program, and "attach" it to the button.

from tkinter import *
from tkinter import ttk


def change():
    print( "change function called" )
    
def main():
    global label
    rootWindow = Tk()

    label = ttk.Label( rootWindow, text="Hello World!" )
    label.pack()

    button1 = ttk.Button( rootWindow, text="Change Label", 
                                    command=change )
    button1.pack()
    
    rootWindow.mainloop()


main()

• Run your code again, and verify that when you click the button, something gets printed in the console.
• Using the console is not necessarily something we want to do with GUI applications, but, in this case, the console is a good way to debug our program and verify that it works as expected.