400 Bad Request in Rest API - Mini Project: Build & Apply

Understanding and Handling 400 Bad Request in REST API

📖 Scenario: You are building a simple REST API that accepts user data. Sometimes, users send incorrect or incomplete data, and your API needs to respond properly with a 400 Bad Request error.

🎯 Goal: Build a small REST API endpoint that checks incoming data and returns a 400 Bad Request response if the data is missing required fields.

📋 What You'll Learn

Create a dictionary called user_data with keys name and email and exact values "Alice" and "[e-mail]"

Create a variable called required_fields that contains a list with "name" and "email"

Write a for loop that checks if each field in required_fields is in user_data

Print "400 Bad Request: Missing {field}" if a required field is missing, otherwise print "200 OK: Data is valid"

💡 Why This Matters

🌍 Real World

APIs often receive data from users or other systems. Validating this data and responding with clear error messages helps keep the system reliable and user-friendly.

💼 Career

Understanding how to handle 400 Bad Request errors is important for backend developers, API designers, and anyone working with web services to ensure robust and clear communication with clients.

1

DATA SETUP: Create user data dictionary

Create a dictionary called user_data with these exact entries: 'name': 'Alice' and 'email': '[e-mail]'

Rest API

# Create the user_data dictionary with name and email
# Your code here

Need a hint?

Use curly braces {} to create a dictionary with keys and values.

2

CONFIGURATION: Define required fields list

Create a variable called required_fields that contains a list with the strings 'name' and 'email'

Rest API

user_data = {'name': 'Alice', 'email': '[e-mail]'}
# Create the required_fields list with 'name' and 'email'
# Your code here

Need a hint?

Use square brackets [] to create a list of required field names.

3

CORE LOGIC: Check for missing fields

Write a for loop using variable field to check if each field in required_fields is present in user_data. If a field is missing, print "400 Bad Request: Missing {field}" and stop checking further.

Rest API

user_data = {'name': 'Alice', 'email': '[e-mail]'}
required_fields = ['name', 'email']
# Write a for loop to check each required field in user_data
# Your code here

Need a hint?

Use for field in required_fields: and check if field not in user_data: inside the loop.

4

OUTPUT: Print success message if all fields present

Add an else block to the for loop that prints "200 OK: Data is valid" if no required fields are missing.

Rest API

user_data = {'name': 'Alice', 'email': '[e-mail]'}
required_fields = ['name', 'email']
for field in required_fields:
    if field not in user_data:
        print(f"400 Bad Request: Missing {field}")
        break
# Add else block to print success message if no fields are missing
# Your code here

Need a hint?

The else after a for loop runs only if the loop did not break.