Python: Variable Scope Made Easy

Stop Getting Lost in Your Code

Last week, I spent three frustrating hours debugging what seemed like a simple function. My variables were mysteriously “undefined” in some places but worked perfectly in others. Sound familiar?

The problem? I didn’t truly understand Python’s scope rules. After diving deep into how Python actually finds and manages variables, those mysterious errors finally made sense. More importantly, I learned powerful patterns like closures that transformed how I write code.

If you’ve ever been confused about where your variables “live” or why some code works in one place but breaks in another, this article will clear everything up. Understanding scope isn’t just about fixing bugs — it’s about writing cleaner, more powerful Python code.

The LEGB Rule

Python follows the LEGB rule to find variables:

• Local: Variables inside the current function
• Enclosing: Variables in outer functions
• Global: Variables at the module level
• Built-in: Python’s predefined variables (like len, print)

Python searches for variables in this exact order.

x = "global"

def outer():
    x = "enclosing"
    
    def…