How to Fix Undefined Variable Errors in Python: A Step‑by‑Step Debugging Guide

Introduction

Hello, I’m PiPi. A few days ago a member of the Python community asked a basic Python question about an undefined variable, and I’m sharing the discussion and solution here.

Problem Overview

The user encountered an error indicating that a variable was not defined. The screenshot below shows the error message.

Implementation Process

Initially it seemed the variable was simply missing, but even after defining it the issue persisted. The following images illustrate the attempted code and the continued errors.

Further investigation revealed that the user had declared a local variable inside a function, included a return statement, but never actually called the function or captured its return value.

Another unrelated error appeared later, as shown below.

Based on the guidance from a community member, the correct approach was to properly define the variable within the function, call the function, and assign its return value.

After applying this fix, the issue was resolved.

Conclusion

This article demonstrated a typical Python beginner problem involving undefined variables and function scope. By analyzing the error messages and applying the proper function call and return handling, the issue was successfully fixed.