Idempotency of methods in Rest API - Mini Project: Build & Apply

Understanding Idempotency of REST API Methods

📖 Scenario: You are building a simple REST API for managing a list of tasks. Each task has an ID and a description. You want to understand how different HTTP methods behave when called multiple times with the same data.

🎯 Goal: Build a simple REST API simulation using Python functions to demonstrate the idempotency of HTTP methods: GET, PUT, POST, and DELETE.

📋 What You'll Learn

Create a dictionary called tasks with initial tasks

Create a variable called new_task with a task description

Write a function put_task that updates or creates a task with a given ID

Write a function post_task that adds a new task with a new ID

Write a function delete_task that deletes a task by ID

Write a function get_task that returns a task by ID

Call each function multiple times to show idempotency behavior

Print the final tasks dictionary

💡 Why This Matters

🌍 Real World

Understanding idempotency helps developers design APIs that behave predictably when clients retry requests, which is common in real-world network communication.

💼 Career

Knowing how HTTP methods behave and their idempotency is essential for backend developers, API designers, and anyone working with web services.

1

Create initial tasks dictionary

Create a dictionary called tasks with these exact entries: 1: 'Buy groceries', 2: 'Read a book', 3: 'Write code'

Rest API

# Create the tasks dictionary with initial tasks
# Your code here

Need a hint?

Use curly braces to create a dictionary with keys 1, 2, and 3 and their task descriptions.

2

Add a new task description variable

Create a variable called new_task and set it to the string 'Go for a walk'

Rest API

tasks = {1: 'Buy groceries', 2: 'Read a book', 3: 'Write code'}
# Create the new_task variable with the value 'Go for a walk'
# Your code here

Need a hint?

Assign the string 'Go for a walk' to the variable new_task.

3

Write functions to simulate HTTP methods

Write four functions: put_task(id, description) to add or update a task, post_task(description) to add a new task with a new ID, delete_task(id) to remove a task, and get_task(id) to return the task description or None if not found. Use the tasks dictionary inside these functions.

Rest API

tasks = {1: 'Buy groceries', 2: 'Read a book', 3: 'Write code'}
new_task = 'Go for a walk'

# Define put_task(id, description) to add or update a task
# Define post_task(description) to add a new task with a new ID
# Define delete_task(id) to remove a task
# Define get_task(id) to return the task description or None
# Your code here

Need a hint?

Use dictionary operations to add, update, delete, and get tasks inside the functions.

4

Call functions to demonstrate idempotency and print tasks

Call put_task(2, 'Read a book') twice, call post_task(new_task) twice, call delete_task(3) twice, then print the tasks dictionary.

Rest API

tasks = {1: 'Buy groceries', 2: 'Read a book', 3: 'Write code'}
new_task = 'Go for a walk'

def put_task(id, description):
    tasks[id] = description

def post_task(description):
    new_id = max(tasks.keys()) + 1 if tasks else 1
    tasks[new_id] = description
    return new_id

def delete_task(id):
    if id in tasks:
        del tasks[id]

def get_task(id):
    return tasks.get(id)

# Call put_task(2, 'Read a book') twice
# Call post_task(new_task) twice
# Call delete_task(3) twice
# Print the tasks dictionary
# Your code here

Need a hint?

Calling put_task twice with the same data does not change the dictionary after the first call (idempotent). Calling post_task twice adds two new tasks (not idempotent). Calling delete_task twice removes the task once and does nothing the second time (idempotent).