Nonlocal keyword in Python - Mini Project: Build & Apply

Understanding the Nonlocal Keyword in Python

📖 Scenario: Imagine you are creating a simple counter inside a function. You want to increase the count each time you call a nested function. This project will help you learn how to use the nonlocal keyword to change a variable in the outer function from inside the inner function.

🎯 Goal: You will build a function with a nested function that increases a counter using the nonlocal keyword. You will then print the updated count.

📋 What You'll Learn

Create a function with a nested function

Use the nonlocal keyword to modify the outer variable

Call the nested function to increase the counter

Print the final counter value

💡 Why This Matters

🌍 Real World

Using <code>nonlocal</code> helps when you want to keep track of changes inside nested functions without using global variables. This is useful in creating counters, stateful functions, or closures.

💼 Career

Understanding <code>nonlocal</code> is important for writing clean, maintainable Python code, especially when working with nested functions, decorators, or advanced function designs.

1

Create the outer function with a counter variable

Create a function called counter that has a variable count set to 0 inside it.

Python

# Create the function counter with count = 0 inside
# Your code here

Need a hint?

Define a function with def counter(): and inside it write count = 0.

2

Add a nested function that uses nonlocal to change count

Inside the counter function, create a nested function called increase. Use the nonlocal keyword for count inside increase. Then add 1 to count inside increase.

Python

def counter():
    count = 0
    # Create nested function increase
    # Use nonlocal count and add 1 to count
    # Your code here

Need a hint?

Inside counter, define def increase():. Use nonlocal count to tell Python you want to change the outer count. Then write count += 1.

3

Call the nested function and return the count

Still inside counter, call the nested function increase() once. Then return the value of count from counter.

Python

def counter():
    count = 0
    def increase():
        nonlocal count
        count += 1
    # Call increase once
    # Return count
    # Your code here

Need a hint?

Call increase() inside counter to add 1 to count. Then use return count to send the updated count back.

4

Print the result of calling counter

Call the function counter() and print its result using print(counter()).

Python

def counter():
    count = 0
    def increase():
        nonlocal count
        count += 1
    increase()
    return count

# Print the result of counter()
# Your code here

Need a hint?

Use print(counter()) to show the number 1, which is the updated count.