Response headers in Flask - Mini Project: Build & Apply

Setting Custom Response Headers in Flask

📖 Scenario: You are building a simple web application using Flask. You want to send a custom response header to the client to provide additional information about the response.

🎯 Goal: Create a Flask route that returns a response with a custom header called X-Custom-Header set to MyValue.

📋 What You'll Learn

Create a Flask app instance named app

Define a route /custom-header that returns a response

Add a custom response header X-Custom-Header with value MyValue

💡 Why This Matters

🌍 Real World

Web developers often need to add custom headers to HTTP responses for security, caching, or metadata purposes.

💼 Career

Understanding how to manipulate response headers is essential for backend developers working with web frameworks like Flask.

1

Create the Flask app and route

Create a Flask app instance called app and define a route /custom-header that returns the string 'Hello, World!'.

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/custom-header')
def custom_header():
    # Your code here

Need a hint?

Use Flask(__name__) to create the app and @app.route('/custom-header') to define the route.

2

Import Response from Flask

Import Response from flask to prepare for creating a response object.

Flask

from flask import Flask, Response

app = Flask(__name__)

@app.route('/custom-header')
def custom_header():
    return 'Hello, World!'  # Modify this to use Response later

Need a hint?

Add Response to the import statement from flask.

3

Create a Response object with custom header

In the custom_header function, create a Response object with the body 'Hello, World!'. Then add a custom header X-Custom-Header with the value MyValue to the response headers.

Flask

from flask import Flask, Response

app = Flask(__name__)

@app.route('/custom-header')
def custom_header():
    response = Response('Hello, World!')
    # Add custom header here
    return response

Need a hint?

Create a Response object and set the header using response.headers['X-Custom-Header'] = 'MyValue'.

4

Run the Flask app

Add the code to run the Flask app with app.run() inside the if __name__ == '__main__': block.

Flask

from flask import Flask, Response

app = Flask(__name__)

@app.route('/custom-header')
def custom_header():
    response = Response('Hello, World!')
    response.headers['X-Custom-Header'] = 'MyValue'
    return response

if __name__ == '__main__':
    # Your code here

Need a hint?

Use the standard Flask app run block to start the server.