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Discover why your Python list `abset` empties after exiting the while loop and learn how to fix it!
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This video is based on the question https://stackoverflow.com/q/73562517/ asked by the user 'jomake' ( https://stackoverflow.com/u/11404259/ ) and on the answer https://stackoverflow.com/a/73562547/ provided by the user 'David_Leber' ( https://stackoverflow.com/u/19882427/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Why Your Python List Becomes Empty After a While Loop abset Explained!

When learning to code in Python, especially while working on projects like a D&D character generator, you might hit some unexpected roadblocks. One common issue that programmers encounter is losing data stored in lists. This problem surfaces particularly when working with functions and loops. One reader recently faced this issue and was puzzled by why their list abset was empty after executing a loop. Let’s walk through the problem and discuss how to troubleshoot and resolve it effectively.

The Problem

In the reader's code, they were rolling four six-sided dice and then dropping the lowest roll to generate ability scores for their character. The primary concern was that despite seeing values being printed during the while loop, the final output stated that the abset list was empty. Here’s an excerpt from their code:

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

Why Does abset Come Out Empty?

The issue arises from how variable scopes work in Python. Here’s a brief breakdown:

Local vs Global Scope: Variables defined inside a function (like abset within the abrl function) are local to that function. They get created when the function is called and cease to exist after the function exits. When you declare abset = list() inside abrl, you’re creating a new abset that only exists within that function.

Global Variable: The abset outside the function is on a global scope, but since the function abrl creates its own local abset, changes made to this local variable do not affect the global abset. Hence, when you try to print the global abset after calling the function, it remains empty.

How to Solve the Problem

To keep the values generated inside the while loop and return them to the global scope, follow these steps:

Step 1: Return the Local abset

At the end of your function, return the populated abset list:

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

Step 2: Store the Returned Values

When you call the abrl() function, store the returned values back into the global abset:

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

Example Final Code

Here’s how the final code will look after applying these fixes:

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

Conclusion

Understanding how variable scopes work is crucial when programming in Python. By putting the right return statements in your functions and correctly handling variable assignments, you can maintain the data you need outside of loops. This approach minimizes confusion and helps ensure that your programs work as expected. Happy coding, and may your dice always roll high!