Скачать или смотреть How to Preserve Variable Values in Python with PyQt5 Buttons

Learn how to maintain variable values across button clicks in your Python PyQt5 application, avoiding issues of variables resetting to zero.
---
This video is based on the question https://stackoverflow.com/q/63077869/ asked by the user 'uckocaman' ( https://stackoverflow.com/u/13325358/ ) and on the answer https://stackoverflow.com/a/63077918/ provided by the user 'Adrien Kaczmarek' ( https://stackoverflow.com/u/13603704/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How do I ensure that the value of the variable is not reset in python?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Preserve Variable Values in Python with PyQt5 Buttons

When working with Python and PyQt5, you might run into a frustrating issue: your variables keep resetting themselves every time you trigger a function. If you’ve faced this problem when trying to count or accumulate values upon button clicks, you’re not alone! In this guide, we’ll take a closer look at why these variables reset and how you can fix this issue effectively. Let's dive in!

The Problem at Hand

Imagine you have a PyQt5 application with a button that should increase counter values every time it's clicked. However, after each click, instead of incrementing the values of x, y, and z, they start back at zero. This can happen if the variables are not being updated correctly within your class. Let's analyze a sample code snippet to see how this problem arises:

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

As you can see, every time the button is clicked, the function onClicked() gets executed. But if you're relying on the global variables x, y, z, they remain at 0, causing you to get unexpected results.

Solution: Using Instance Variables

To resolve this issue, you should rely on instance variables (attributes that belong to the class) instead of global variables. Here’s how you can adjust your code to maintain the counter values across function calls.

Step-by-Step Solution

Remove Global Declarations: You can eliminate the global declarations, as you’re not using them effectively in this context.

Initialize Instance Variables: The constructor (__init__) of the class should initialize your instance variables.

Update Instance Variables: Make sure to update and access the instance variables (self.x, self.y, self.z) properly within your onClicked method.

Here’s the corrected version of your code:

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

Key Changes Explained

No Use of Global Variables: By removing references to the global variables, you significantly reduce the risk of them being reset unexpectedly.

Using self.x, self.y, self.z: These variables are now correctly tied to the instance of your main window class, meaning they keep their values as long as that instance exists.

Print Updated Values: Now, when you print self.x, self.y, and self.z in the onClicked method, you’ll see the correctly incremented values every time the button is pressed!

Conclusion

By following these steps, you can ensure that your variable values are preserved across function calls in a PyQt5 application. Remember, utilizing instance variables is a fundamental part of using classes in Python, allowing you to keep track of state within your applications. Happy coding!