Using the Tkinter User Interface: A Quick Introduction

What is Tkinter?

Tkinter is the Python interface to the Tcl/Tk GUI toolkit (hence the name Tkinter)

The TclTk GUI toolkit works across a number of windowing systems (Mac, Windows, Linux, etc)

Tkinter is pronounced a whole bunch of ways:

T-K-inter T�kinter, and others (seems like most call it T-K-inter)

Tkinter is included in Python distributions (like Anaconda) and is very popular

It provides Python developers with a relatively easy handle to the graphical user interface (GUI) of the native operating system (Linux, Mac OS, Windows, etc)

You can use Tkinter to draw, browse for files, and do just about everything you see in a modern GUI application

This code (from http://effbot.org/tkinterbook/canvas.htm) creates a window, adds a canvas, and draws on it

This code (from http://tkinter.unpythonic.net/wiki/tkFileDialog) creates a window and populates it with buttons that interact with the file system

As you can see from these 2 samples, you can approach Tkinter in very different ways

Designing and building programs for an event driven environment

After setup, your program doesn�t �do� anything until it gets an event (like a button push, etc)

Actions in your program are initiated by user requests

The design of the program starts with a good user interface

A crash course in Tkinter and event driven processing

GUIs use an event handling model to respond to user and OS-level actions

Types of events include painting requests, mouse clicks or drags, text entry, and so on

An event driven program spends most of its time in a message loop that waits for the OS to send it event notifications (Hey�you got a mouse click) and related details (the mouse click happened at x=348, y=212)

The message loop sends the notification to the appropriate handler in your program

Let�s look at a relatively small program that adds 1 button to a frame and interacts with it

This example comes from http://effbot.org/tkinterbook/button.htm

Clicking on the button causes Click! to be printed in the console window

The program, line by line:

# Import the Tkinter module:

from Tkinter import *

# Create the main window (master):

master = Tk()

# Create an event handler (a �callback� function)

# called callback() to handle mouse clicks:

def callback():

print "click!"

# Construct an object b of the Button class that will be

# placed on master, is labeled OK, and is associated

# with the event handler callback()

b = Button(master, text="OK", command=callback)

# run the layout manager to actually place the button on master

b.pack()

# Start the message handling loop

mainloop()

Some notes on names and conventions:

You don�t have to name a callback function callback()�you can call it anything you want

Although master is a conventional name for a main window, root is also used frequently

Be conventional, however; use a name that people will recognize

Here is an extension of the previous example with 2 buttons

There are now 2 handlers (callbacks); one for each button

This is a simple working program for calculating the earth distance along a line of latitude

It�s functionally identical to the Java program described here but uses better exception handling