Flask Request and Response

1. Setting Up Flask

Step 1: Install Flask (If Not Installed)

pip install flask

Now, create a project folder and navigate into it:

mkdir flask_request_response
cd flask_request_response

2. Handling GET Requests

Step 2: Create a Basic Flask App

Create a file named app.py and add the following code:

from flask import Flask, request

app = Flask(__name__)

@app.route("/", methods=["GET"])
def home():
    return "Welcome to Flask Request and Response Tutorial!"

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

Run the Flask app and visit http://127.0.0.1:5000/ in your browser. You should see

Welcome to Flask Request and Response Tutorial!

3. Handling Query Parameters

Step 3: Retrieve Query Parameters from a URL

Modify app.py to capture query parameters:

@app.route("/search", methods=["GET"])
def search():
    query = request.args.get("q")
    return f"Search results for: {query}"

Now, visit http://127.0.0.1:5000/search?q=Flask and see the response:

Search results for: Flask

4. Handling POST Requests with Form Data

Step 4: Handling Form Submissions

Modify app.py to accept form data via POST requests:

@app.route("/submit", methods=["POST"])
def submit():
    name = request.form.get("name")
    email = request.form.get("email")
    return f"Received data: Name = {name}, Email = {email}"

5. Handling JSON Data in Requests

Step 5: Accepting JSON Data

Modify app.py to handle JSON data:

import json

@app.route("/json", methods=["POST"])
def json_data():
    data = request.get_json()
    return json.dumps({"message": "Received!", "data": data})

To test, send a POST request with JSON data using Postman or cURL:

curl -X POST http://127.0.0.1:5000/json -H "Content-Type: application/json" -d '{"name": "Zia", "role": "Developer"}'

6. Customizing Flask Responses

Step 6: Sending Custom Responses

Modify app.py to create a custom response:

from flask import jsonify, make_response

@app.route("/custom_response")
def custom_response():
    response = make_response(jsonify({"message": "Custom Response"}), 200)
    response.headers["Content-Type"] = "application/json"
    return response

7. Handling Status Codes

Step 7: Returning Different HTTP Status Codes

Modify app.py to return error codes when necessary:

@app.route("/error")
def error():
    return jsonify({"error": "Something went wrong!"}), 400

Now, visit http://127.0.0.1:5000/error, and you'll get:

{
    "error": "Something went wrong!"
}

Conclusion

In this guide, you’ve learned how to:

✅ Handle GET and POST requests
✅ Retrieve query parameters and form data
✅ Process JSON requests
✅ Customize responses and status codes

Flask’s request and response handling makes it easy to build interactive web applications. Now, you can move forward with API development and advanced request handling in Flask! 🚀

PYTHON FLASK