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Python GUI Programming - A Complete Reference Guide

You're reading from   Python GUI Programming - A Complete Reference Guide Develop responsive and powerful GUI applications with PyQt and Tkinter

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Product type Course
Published in Jun 2019
Publisher Packt
ISBN-13 9781838988470
Length 746 pages
Edition 1st Edition
Languages
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Authors (2):
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B. M. Harwani B. M. Harwani
Author Profile Icon B. M. Harwani
B. M. Harwani
Alan D. Moore Alan D. Moore
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Alan D. Moore
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Table of Contents (28) Chapters Close

Title Page
Copyright About Packt Contributors Preface 1. Introduction to Tkinter FREE CHAPTER 2. Designing GUI Applications with Tkinter 3. Creating Basic Forms with Tkinter and ttk Widgets 4. Reducing User Error with Validation and Automation 5. Planning for the Expansion of Our Application 6. Creating Menus with Menu and Tkinter Dialogs 7. Navigating Records with Treeview 8. Improving the Look with Styles and Themes 9. Creating Automated Tests with unittest 10. Improving Data Storage with SQL 11. Connecting to the Cloud 12. Visualizing Data Using the Canvas Widget 13. Creating a User Interface with Qt Components 14. Event Handling - Signals and Slots 15. Understanding OOP Concepts 16. Understanding Dialogs 17. Understanding Layouts 18. Networking and Managing Large Documents 19. Database Handling 20. Using Graphics 21. Implementing Animation 22. Using Google Maps 1. Other Books You May Enjoy

Validation in Tkinter

Tkinter's validation system is one of those parts of the toolkit that is less than intuitive. It relies on the following three configuration options that we can pass into any input widget:

  • validate: This option determines which type of event will trigger the validation callback
  • validatecommand: This option takes the command that will determine if the data is valid
  • invalidcommand: This option takes a command that will run if validatecommand returns False

This seems pretty straightforward, but there are some unexpected curves.

The values we can pass to validate are as follows:

Validates string Triggers when
none It is none that turns off validation
focusin The user enters or selects the widget
unfocus The user leaves the widget
focus Either focusin or focusout
key The user enters text in the widget
all focusin, focusout, and key

 ...

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