Have you heard of the nonlocal keyword in Python?

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When working with nested functions in Python, you might encounter situations where you need to modify a variable defined in an enclosing scope. This is where the nonlocal keyword comes into play. In this post, we’ll explore what nonlocal is, how it works, and when to use it.

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What Is nonlocal?

The nonlocal statement is used to indicate that a variable exists in an enclosing scope (but not the global scope) and should be rebound in that scope. It allows you to modify the value of a variable from a parent function inside a nested function.

Syntax

nonlocal variable_name

This simple statement tells Python to look for the variable in the nearest enclosing scope that is not the global scope.

Why do we need nonlocal?

Here’s an example to demonstrate its usage:

def outer_function():
    x = 10  # This variable is in the enclosing scope of inner_function
    
    def inner_function():
        nonlocal x
        x += 1
        print("Inner x:", x)
    
    inner_function()
    print("Outer x:", x)…