Flask REST API Basics

1. Setting Up Flask

Step 1: Install Flask

Ensure you have Flask installed or install it using pip:

pip install flask

2. Creating a Flask App

Step 2: Initialize Flask

Create a file app.py and set up the basic Flask application:

from flask import Flask, jsonify

app = Flask(__name__)

@app.route("/", methods=["GET"])
def home():
    return jsonify({"message": "Welcome to the Flask REST API!"})

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

Run the app using python app.py.
Open a browser and visit http://127.0.0.1:5000/ to see the JSON response.

3. Creating a Sample Data Model

Step 3: Define Sample Data

For this guide, we will use a simple list to store books instead of a database:

books = [
    {"id": 1, "title": "Flask for Beginners", "author": "John Doe"},
    {"id": 2, "title": "Advanced Flask", "author": "Jane Smith"}
]

4. Implementing CRUD Operations

Step 4: Get All Books (GET Request)

@app.route("/books", methods=["GET"])
def get_books():
    return jsonify(books)

Visit http://127.0.0.1:5000/books in the browser to see the list of books.

Step 5: Get a Single Book by ID

@app.route("/books/<int:book_id>", methods=["GET"])
def get_book(book_id):
    book = next((b for b in books if b["id"] == book_id), None)
    return jsonify(book) if book else jsonify({"error": "Book not found"}), 404

Visit http://127.0.0.1:5000/books/1 to fetch a specific book.

Step 6: Add a New Book (POST Request)

from flask import request

@app.route("/books", methods=["POST"])
def add_book():
    new_book = request.get_json()
    books.append(new_book)
    return jsonify(new_book), 201

Use Postman or cURL to send a POST request with JSON data like this:

{
    "id": 3,
    "title": "Flask REST API Guide",
    "author": "Mike Lee"
}

Step 7: Update an Existing Book (PUT Request)

@app.route("/books/<int:book_id>", methods=["PUT"])
def update_book(book_id):
    book = next((b for b in books if b["id"] == book_id), None)
    if not book:
        return jsonify({"error": "Book not found"}), 404

    data = request.get_json()
    book.update(data)
    return jsonify(book)

Use Postman or cURL to send a PUT request with updated data.

Step 8: Delete a Book (DELETE Request)

@app.route("/books/<int:book_id>", methods=["DELETE"])
def delete_book(book_id):
    global books
    books = [b for b in books if b["id"] != book_id]
    return jsonify({"message": "Book deleted successfully"})

Visit http://127.0.0.1:5000/books/1 and send a DELETE request.

Visit http://127.0.0.1:5000/books/1 and send a DELETE request.

5. Running and Testing the API

Run the Flask app using:

python app.py

Use Postman or cURL to send requests and verify the API responses.

Conclusion

In this guide, you learned how to:

✅ Set up a Flask REST API
✅ Create GET, POST, PUT, and DELETE routes
✅ Use Flask’s request and jsonify modules
✅ Handle CRUD operations with a simple in-memory dataset

This is a basic setup for Flask REST APIs, and you can extend it by integrating databases, authentication, and middleware. 🚀

PYTHON FLASK