Response object creation in Flask

Introduction

A response object in Flask is what your web app sends back to the user's browser. It tells the browser what to show or do next.

When you want to send a simple message or HTML page back to the user.

When you need to send a file or image as a response.

When you want to customize the status code or headers of the response.

When you want to redirect the user to another page.

When you want to return JSON data from an API endpoint.

Syntax

Flask

from flask import Response

response = Response(response=None, status=None, headers=None, mimetype=None, content_type=None, direct_passthrough=False)

The response parameter is the content you want to send back, like text or HTML.

You can set status to a number like 200 (OK) or 404 (Not Found).

Examples

This creates a plain text response with the message "Hello, world!" and status code 200.

Flask

from flask import Response

resp = Response("Hello, world!", status=200, mimetype='text/plain')

This sends back HTML content to show a heading.

Flask

from flask import Response

resp = Response("<h1>Welcome</h1>", mimetype='text/html')

This adds a custom header to the response.

Flask

from flask import Response

headers = {'X-Custom-Header': 'MyValue'}
resp = Response("Data", headers=headers)

This creates a response with no content but a 404 Not Found status.

Flask

from flask import Response

resp = Response(status=404)

Sample Program

This Flask app sends a simple HTML heading as a response when you visit the home page.

Flask

from flask import Flask, Response

app = Flask(__name__)

@app.route('/')
def home():
    content = "<h1>Hello from Flask!</h1>"
    return Response(content, status=200, mimetype='text/html')

if __name__ == '__main__':
    app.run(debug=True)

Important Notes

Use mimetype or content_type to tell the browser what kind of content you are sending.

Always set the correct status code to help browsers and tools understand the response.

Flask also provides shortcut functions like flask.jsonify and flask.redirect for common response types.

Summary

A Response object is what Flask sends back to the user's browser.

You can customize the content, status code, headers, and content type.

Creating a Response object lets you control exactly what the user receives.