File download responses in Flask - Mini Project: Build & Apply

File Download Responses with Flask

📖 Scenario: You are building a simple web app using Flask. The app should allow users to download a text file when they visit a specific URL.

🎯 Goal: Create a Flask app that sends a file download response with a text file named example.txt containing some content.

📋 What You'll Learn

Create a Flask app instance named app

Create a route /download that triggers the file download

Use Flask's Response object to send the file content

Set the correct headers to make the browser download the file as example.txt

💡 Why This Matters

🌍 Real World

Web apps often need to let users download files like reports, images, or documents. This project shows how to send such files correctly.

💼 Career

Backend developers frequently implement file download endpoints. Knowing how to set response headers properly is essential for user-friendly downloads.

1

Set up Flask app and file content

Import Flask and create a Flask app instance called app. Then create a variable file_content with the string value 'Hello, this is a sample file for download.'.

Flask

# Your code here

Need a hint?

Start by importing Flask and creating the app instance. Then assign the exact string to file_content.

2

Create download route and import Response

Import Response from flask. Then create a route /download using @app.route('/download') and define a function download_file().

Flask

from flask import Flask
from flask import Response

app = Flask(__name__)

file_content = 'Hello, this is a sample file for download.'

# Create route /download and function download_file
# Your code here

Need a hint?

Remember to import Response and use the exact route and function names.

3

Create Response with file content and headers

Inside download_file(), create a Response object named response with file_content as data and mimetype='text/plain'. Then set the header Content-Disposition to 'attachment; filename=example.txt' on response.headers. Finally, return response.

Flask

from flask import Flask
from flask import Response

app = Flask(__name__)

file_content = 'Hello, this is a sample file for download.'

@app.route('/download')
def download_file():
    # Create Response with file_content and mimetype
    # Set Content-Disposition header
    # Return response
    # Your code here

Need a hint?

Use the Response constructor with the file content and set the header exactly as shown.

4

Add app run block for local testing

Add the standard Flask app run block: if __name__ == '__main__': and inside it call app.run(debug=true).

Flask

from flask import Flask
from flask import Response

app = Flask(__name__)

file_content = 'Hello, this is a sample file for download.'

@app.route('/download')
def download_file():
    response = Response(file_content, mimetype='text/plain')
    response.headers['Content-Disposition'] = 'attachment; filename=example.txt'
    return response

# Add app run block below
# Your code here

Need a hint?

This block allows you to run the Flask app locally for testing.