Book Image

Tkinter GUI Application Development Blueprints

By : Bhaskar Chaudhary
Book Image

Tkinter GUI Application Development Blueprints

By: Bhaskar Chaudhary

Overview of this book

Tkinter is the built-in GUI package that comes with standard Python distributions. It is a cross-platform package, which means you build once and deploy everywhere. It is simple to use and intuitive in nature, making it suitable for programmers and non-programmers alike. This book will help you master the art of GUI programming. It delivers the bigger picture of GUI programming by building real-world, productive, and fun applications such as a text editor, drum machine, game of chess, media player, drawing application, chat application, screen saver, port scanner, and many more. In every project, you will build on the skills acquired in the previous project and gain more expertise. You will learn to write multithreaded programs, network programs, database driven programs and more. You will also get to know the modern best practices involved in writing GUI apps. With its rich source of sample code, you can build upon the knowledge gained with this book and use it in your own projects in the discipline of your choice.
Table of Contents (15 chapters)
Tkinter GUI Application Development Blueprints
About the Author
About the Reviewers

Handling widget-specific variables

You need variables with a wide variety of widgets. You likely need a string variable to track what the user enters into the entry widget or text widget. You most probably need Boolean variables to track whether the user has checked off the Checkbox widget. You need integer variables to track the value entered in a Spinbox or Slider widget.

In order to respond to changes in widget-specific variables, Tkinter offers its own variable class. The variable that you can use to track widget-specific values must be subclassed from this Tkinter variable class. Tkinter offers some commonly used predefined variables. They are StringVar, IntVar, BooleanVar, and DoubleVar.

You can use these variables to capture and play with the changes in the values of variables from within your callback functions. You can also define your own variable type, if required.

Creating a Tkinter variable is simple. You simply have to call the constructor:

my_string = StringVar()
ticked_yes = BooleanVar()
group_choice = IntVar()
volume = DoubleVar()

Once the variable is created, you can use it as a widget option, as follows:

Entry(root, textvariable=my_string)
Checkbutton(root, text="Remember Me", variable=ticked_yes)
Radiobutton(root, text="Option1", variable=group_choice, value="option1") #radiobutton
Scale(root, label="Volume Control", variable=volume, from =0, to=10) # slider

Additionally, Tkinter provides access to the values of variables via the set() and get() methods, as follows:

my_var.set("FooBar") # setting value of variable
my_var.get() # Assessing the value of variable from say a callback

A demonstration of the Tkinter variable class is available in the code file. The code generates a window, as shown in the following screenshot:

This concludes our brief discussion on events and callbacks. Here's a brief summary of the things that we discussed:

  • The command binding, which is used to bind simple widgets to certain functions

  • The use of the lambda function in case you need to process arguments

  • Event binding using the widget.bind(event, callback, add=None) method to bind keyboard and mouse events to your widgets and invoke callbacks when certain events occur

  • The passing of extra arguments to a callback

  • The binding of events to an entire application or to a particular class of widget by using bind_all() and bind_class()

  • Using the Tkinter variable class to set and get the values of widget-specific variables

In short, you now know how to make your GUI program responsive to end-user requests!