POST for creating resources in Rest API - Mini Project: Build & Apply

POST for Creating Resources

📖 Scenario: You are building a simple web service that allows users to add new books to a library collection. The service will accept data about books and store them.

🎯 Goal: Create a REST API endpoint that accepts POST requests to add new books to the library collection. You will build the data structure, configure the endpoint, implement the POST logic, and finally test the output.

📋 What You'll Learn

Create a list called library to store book data

Create a configuration variable next_id to assign unique IDs to books

Implement a POST endpoint /books that accepts JSON data with title and author

Add the new book with a unique id to the library list

Return the newly created book data as JSON in the response

💡 Why This Matters

🌍 Real World

Creating REST APIs to add resources is common in web services like online stores, libraries, and social media platforms.

💼 Career

Understanding how to handle POST requests and create resources is essential for backend developers and API designers.

1

Create the initial data structure

Create a list called library that will hold dictionaries representing books. Start with an empty list.

Rest API

# Create an empty list called library
# Your code here

Hint

Use library = [] to create an empty list.

2

Add a configuration variable for unique IDs

Create a variable called next_id and set it to 1. This will be used to assign unique IDs to new books.

Rest API

library = []
# Create a variable next_id and set it to 1
# Your code here

Hint

Use next_id = 1 to start counting book IDs from 1.

3

Implement the POST endpoint logic

Write a function called add_book that takes a dictionary book_data with keys title and author. Inside the function, use the global variable next_id. Create a new dictionary with keys id, title, and author. Assign id the value of next_id. Append this new dictionary to the library list. Increment next_id by 1. Return the new book dictionary.

Rest API

library = []
next_id = 1

def add_book(book_data):
    # Your code here

Hint

Remember to use global next_id to modify the variable inside the function.

4

Test the POST endpoint function output

Call the function add_book with the dictionary {'title': '1984', 'author': 'George Orwell'}. Print the returned value.

Rest API

library = []
next_id = 1

def add_book(book_data):
    global next_id
    new_book = {
        'id': next_id,
        'title': book_data['title'],
        'author': book_data['author']
    }
    library.append(new_book)
    next_id += 1
    return new_book

# Call add_book with the given dictionary and print the result
# Your code here

Hint

Use print(add_book({'title': '1984', 'author': 'George Orwell'})) to see the new book added.

Practice

1. What is the primary purpose of the POST method in REST APIs?

easy

A. To create a new resource on the server

B. To retrieve data from the server

C. To update an existing resource completely

D. To delete a resource from the server

Solution

1. Step 1: Understand HTTP methods

   HTTP methods have specific roles: GET retrieves, POST creates, PUT updates, DELETE removes.

2. Step 2: Identify POST's role

   POST sends data to the server to create a new resource, unlike GET which only fetches data.

3. Final Answer:

   To create a new resource on the server -> Option A

4. Quick Check:

   POST = Create resource [OK]

Hint: POST is for sending data to create something new [OK]

Common Mistakes:

• Confusing POST with GET which only fetches data
• Thinking POST updates existing resources fully
• Assuming POST deletes resources

2. Which of the following is the correct way to send data in a POST request to create a resource?

easy

A. Include data in the URL query parameters

B. Send data in the request body as JSON

C. Send data as HTTP headers

D. Send data as a cookie

Solution

1. Step 1: Identify where POST data goes

   POST requests send data in the request body, not in URL or headers.

2. Step 2: Recognize common data format

   JSON is the standard format for sending structured data in the body for REST APIs.

3. Final Answer:

   Send data in the request body as JSON -> Option B

4. Quick Check:

   POST data = request body JSON [OK]

Hint: POST data goes in the body, not URL or headers [OK]

Common Mistakes:

• Putting data in URL query instead of body
• Trying to send data via headers
• Using cookies to send creation data

3. Given this Python code using the requests library, what will be the HTTP status code if the resource is created successfully?

import requests
url = 'https://api.example.com/items'
data = {'name': 'Book', 'price': 12.99}
response = requests.post(url, json=data)
print(response.status_code)

medium

A. 200

B. 404

C. 201

D. 500

Solution

1. Step 1: Understand POST success codes

   When a resource is created, the server usually returns HTTP status 201 Created.

2. Step 2: Analyze the code behavior

   The code sends a POST request with JSON data; if successful, response.status_code will be 201.

3. Final Answer:

   201 -> Option C

4. Quick Check:

   POST success = 201 Created [OK]

Hint: 201 means resource created successfully [OK]

Common Mistakes:

• Confusing 200 OK with 201 Created
• Assuming 404 means success
• Thinking 500 means success

4. You wrote this POST request code but get a 400 Bad Request error. What is the likely problem?

import requests
url = 'https://api.example.com/users'
data = {'username': 'alice'}
response = requests.post(url, data=data)
print(response.status_code)

medium

A. The data should be sent as JSON, not form data

B. The URL is incorrect for POST requests

C. POST requests cannot send data

D. The server does not support HTTPS

Solution

1. Step 1: Check data sending method

   Using data=data sends form-encoded data, but API expects JSON for POST creation.

2. Step 2: Fix data format

   Use json=data in requests.post to send JSON body, which the server accepts.

3. Final Answer:

   The data should be sent as JSON, not form data -> Option A

4. Quick Check:

   Send JSON with json= parameter [OK]

Hint: Use json= not data= to send JSON body [OK]

Common Mistakes:

• Sending form data instead of JSON
• Assuming URL is wrong without checking
• Thinking POST can't send data
• Ignoring HTTPS requirement

5. You want to create a new blog post resource with title and content using a POST request. Which of these JSON payloads correctly represents the data to send in the request body?

hard

A. ["title", "My Day", "content", "It was sunny."]

B. "title=My Day&content=It was sunny."

C. {"My Day": "title", "It was sunny.": "content"}

D. {"title": "My Day", "content": "It was sunny."}

Solution

1. Step 1: Understand JSON object structure

   JSON objects use key-value pairs with keys as strings and values as data.

2. Step 2: Identify correct JSON format

   {"title": "My Day", "content": "It was sunny."} correctly uses keys "title" and "content" with their string values in an object.

3. Final Answer:

   {"title": "My Day", "content": "It was sunny."} -> Option D

4. Quick Check:

   JSON object with keys and values = {"title": "My Day", "content": "It was sunny."} [OK]

Hint: JSON data must be key-value pairs inside braces {} [OK]

Common Mistakes:

• Using JSON arrays instead of objects
• Swapping keys and values
• Sending URL-encoded string instead of JSON