Python Coding challenge - Day 1138| What is the output of the following Python Code?

 

Code Explanation:

🧩 1. Function Definition: outer

def outer():

This defines a function named outer.

It acts as an enclosing (parent) function.

📦 2. Variable Initialization

    x = 10

A local variable x is created inside outer.

Initial value of x is 10.

🔁 3. Inner Function Definition

    def inner():

A nested function named inner is defined inside outer.

It has access to variables of outer (like x).

🔗 4. Using nonlocal

        nonlocal x

nonlocal means:

“Use the variable x from the nearest enclosing scope (outer function), not create a new one.”

Without nonlocal, modifying x would cause an error.

➕ 5. Modify the Variable

        x += 5

Adds 5 to the existing value of x.

Since x is nonlocal, it updates the outer function’s x.

🔙 6. Return Updated Value

        return x

Returns the updated value of x.

📤 7. Return Inner Function

    return inner

The outer function returns the inner function itself, not its result.

This creates a closure (function + its environment).

🎯 8. Create Function Instance

f = outer()

Calls outer(), which returns inner.

Now f becomes a reference to inner, with x = 10 preserved.

🖨️ 9. Function Calls and Output

print(f(), f())

First Call: f()

x = 10

x += 5 → 15

Returns 15

Second Call: f()

x = 15 (value persists due to closure)

x += 5 → 20

Returns 20

✅ Final Output

15 20

Book: 900 Days Python Coding Challenges with Explanation