Solve the Issue of tkinter Comboboxes Sharing Values in Your GUI App

Discover how to prevent two `tkinter` comboboxes in your Python GUI app from sharing the same value with this clear and practical guide.
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This video is based on the question stackoverflow.com/q/71550260/ asked by the user 'User19' ( stackoverflow.com/u/13635559/ ) and on the answer stackoverflow.com/a/71550668/ provided by the user 'furas' ( stackoverflow.com/u/1832058/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the Issue of Two tkinter Comboboxes Always Getting the Same Value

When you're building a graphical user interface (GUI) using Python's tkinter library, you may encounter a common problem: two comboboxes appear to be synchronized, meaning changing the value in one combobox automatically changes it in the other. This can be frustrating, especially when you want each combobox to operate independently. In this guide, we'll explore the underlying cause of this issue and provide a straightforward solution to ensure both comboboxes function as intended.

Understanding the Problem

In the provided code snippet, there are two comboboxes, source_options and destination_options, initialized with the same list of values. The main issue arises from the way the textvariable attribute is being used. Instead of associating each combobox with a unique StringVar, both are being linked to a shared list. Consequently, any change made to one combobox propagates to the other, causing them to always display the same value.

Example of the Problematic Code

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

The Solution

Step-by-Step Guide

To resolve the issue, we need to properly utilize the textvariable attribute by creating separate StringVar instances for each combobox. This will ensure that the values are stored independently. Here’s how to implement the solution:

Create StringVar Instances: For each combobox, create an instance of StringVar. This object will store the value of the selected item.

Assign the StringVar to textvariable: Link each combobox to its respective StringVar so that changes in one do not affect the other.

Updated Code

Here's the corrected version of the code demonstrating the solution:

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

Additional Notes

If your intention is simply to retrieve values from the comboboxes without needing to track their state, you can omit the textvariable altogether. Instead, you can fetch the current selection directly from the combobox when needed, as shown in the on_press method.

Conclusion

By ensuring that each combobox has its own separate StringVar, you can easily resolve the issue of shared values. This change allows your GUI application to function correctly, with each combobox operating independently. Now, not only can you successfully implement multiple comboboxes in your tkinter application, but you can also manage user inputs effectively. Happy coding!