How to Effectively Validate CustomTkinter Entry Without invalidcommand

Learn how to validate user input in `CustomTkinter` entry fields effectively, even without the `invalidcommand` feature. This guide provides a simple solution and structured logic to enhance your GUI applications.
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This video is based on the question https://stackoverflow.com/q/77444695/ asked by the user 'Jan_B' ( https://stackoverflow.com/u/22326950/ ) and on the answer https://stackoverflow.com/a/77444696/ provided by the user 'Jan_B' ( https://stackoverflow.com/u/22326950/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Effectively Validate CustomTkinter Entry Without invalidcommand

When transitioning an application from classic tkinter to customtkinter, developers often encounter challenges, particularly with input validation. One common roadblock is the absence of the invalidcommand feature in CTkEntry, which can complicate user experience design. This guide will explore an effective method for validating entry inputs in customtkinter without relying on the invalidcommand.

The Problem

In classic tkinter, the input validation process could effectively utilize invalidcommand to reset an entry field or provide feedback when input was incorrect. However, when using customtkinter, this feature is missing, leading many developers to ponder their options.

Here's a scenario:

You have an entry widget that requires specific input formatted as 02200000 (a mandatory structure).

If users enter anything else, you want to configure the entry to revert to the default value of 02200000.

You might wonder: How can we replicate this functionality in customtkinter?

The Solution

Through some experimentation, a straightforward solution emerges: we can incorporate the reset logic directly within the validation function. Let's break down the approach.

Step 1: Structure Your Main Application

Create a basic application structure using customtkinter, ensuring that you register the validation function within the entry:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Implement the Validation Function

This function will now not only validate the input but also reset it if the input does not match the specified pattern:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Handle Valid Inputs

Now, we need a way to process valid inputs:

[[See Video to Reveal this Text or Code Snippet]]

Complete Code Example

Here’s the complete code for your reference:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By embedding the reset functionality directly in the validation function, you can maintain control over the user inputs effectively in customtkinter. As an added benefit, you simplify your logic without overcrowding your application with unnecessary function calls.

Feel free to expand upon this foundation and adapt the validation and processing logic to cater to your application’s needs!