500 Internal Server Error in Rest API - Mini Project: Build & Apply

Handling 500 Internal Server Error in a REST API

📖 Scenario: You are building a simple REST API for a bookstore. Sometimes, unexpected errors happen on the server, causing a 500 Internal Server Error. You want to handle this error gracefully and return a friendly message to the user.

🎯 Goal: Build a small REST API using Flask that simulates a 500 Internal Server Error and handles it by returning a clear JSON message.

📋 What You'll Learn

Create a Flask app with a route /books

Add a configuration variable simulate_error to control error simulation

Use a try-except block to simulate and catch the 500 Internal Server Error

Return a JSON response with an error message when the error occurs

💡 Why This Matters

🌍 Real World

Web servers often face unexpected problems. Handling 500 Internal Server Errors gracefully helps users understand that something went wrong without exposing technical details.

💼 Career

Backend developers must know how to handle server errors properly to build reliable and user-friendly APIs.

1

Create the Flask app and /books route

Write code to import Flask, create an app called app, and add a route /books that returns a list of book titles as JSON.

Rest API

from flask import Flask, jsonify

app = Flask(__name__)

# Create a route '/books' that returns a JSON list of books
# Your code here

Need a hint?

Use @app.route('/books') to create the route and return a JSON list using jsonify.

2

Add a configuration variable simulate_error

Add a variable called simulate_error and set it to True to simulate a server error.

Rest API

from flask import Flask, jsonify

app = Flask(__name__)
simulate_error = True  # Add this variable to control error simulation

@app.route('/books')
def books():
    return jsonify(['The Hobbit', '1984', 'Pride and Prejudice'])

Need a hint?

Just create a variable simulate_error and set it to True.

3

Simulate and handle the 500 Internal Server Error

Modify the books function to use a try-except block. If simulate_error is True, raise an Exception. Catch the exception and return a JSON response with {'error': 'Internal Server Error'} and status code 500.

Rest API

from flask import Flask, jsonify

app = Flask(__name__)
simulate_error = True

@app.route('/books')
def books():
    # Use try-except to simulate and handle error
    # Your code here

Need a hint?

Use try and except Exception to catch errors. Raise an exception if simulate_error is True.

4

Run the app and print the error response

Add code to run the Flask app only if the file is run directly. Then, simulate a request to /books and print the JSON response and status code.

Rest API

from flask import Flask, jsonify

app = Flask(__name__)
simulate_error = True

@app.route('/books')
def books():
    try:
        if simulate_error:
            raise Exception('Simulated server error')
        return jsonify(['The Hobbit', '1984', 'Pride and Prejudice'])
    except Exception:
        return jsonify({'error': 'Internal Server Error'}), 500

if __name__ == '__main__':
    # Run the app and print the response from /books
    # Your code here

Need a hint?

Use app.test_client() to simulate a request and print response.json and response.status_code.