Enclosing scope in Python - Mini Project: Build & Apply

Understanding Enclosing Scope with Nested Functions

📖 Scenario: Imagine you are creating a simple calculator that can add a fixed number to any input number. You want to keep the fixed number hidden inside the calculator so it cannot be changed directly.

🎯 Goal: Build a nested function where the inner function uses a number from the outer function's scope (enclosing scope) to add to its input.

📋 What You'll Learn

Create an outer function called make_adder that takes one parameter fixed_number.

Inside make_adder, define an inner function called adder that takes one parameter num.

The inner function adder should return the sum of num and fixed_number from the enclosing scope.

The outer function make_adder should return the inner function adder.

Create a variable add_five by calling make_adder(5).

Call add_five(10) and print the result.

💡 Why This Matters

🌍 Real World

Enclosing scope is used in real-world programming to create functions that remember settings or data without using global variables.

💼 Career

Understanding enclosing scope helps in writing clean, reusable code and is important for jobs involving Python programming, especially in web development and data science.

1

Create the outer function make_adder with parameter fixed_number

Write a function called make_adder that takes one parameter called fixed_number. Inside it, define an inner function called adder that takes one parameter called num. Do not write the inner function body yet.

Python

def make_adder(fixed_number):
    def adder(num):
        # Your code here

Need a hint?

Remember to indent the inner function adder inside make_adder.

2

Make the inner function adder return the sum of num and fixed_number

Inside the inner function adder, write a return statement that adds num and fixed_number from the enclosing scope.

Python

def make_adder(fixed_number):
    def adder(num):
        # Your code here

Need a hint?

Use return num + fixed_number to add the inner parameter and the outer parameter.

3

Make make_adder return the inner function adder

Add a return statement at the end of make_adder that returns the inner function adder (without calling it).

Python

def make_adder(fixed_number):
    def adder(num):
        return num + fixed_number
    # Your code here

Need a hint?

Return the inner function adder itself, not the result of calling it.

4

Create add_five and print the result of add_five(10)

Create a variable called add_five by calling make_adder(5). Then call add_five(10) and print the result.

Python

def make_adder(fixed_number):
    def adder(num):
        return num + fixed_number
    return adder

# Your code here

Need a hint?

Calling add_five(10) should add 5 to 10 and print 15.