🧩 What You’ll Build
We’ll create a Book Management API with endpoints to:
Get all books
Get a book by ID
Add a new book
Update a book
Delete a book
All data will be stored in a simple in-memory list (you can later connect it to a database like SQLite or PostgreSQL).
⚙️ Step 1: Setup Your Environment
1️⃣ Install Flask
pip install flask
(Optional but recommended)
pip install flask-cors
flask-cors lets your API handle requests from different domains — useful when connecting to a frontend (e.g., React, Vue, Angular).
📁 Step 2: Create Project Structure
flask_api/
│
├── app.py # Main application file
├── requirements.txt # Dependencies
└── README.md
🧠 Step 3: Build the Basic Flask App
Open app.py and start with a minimal Flask setup:
from flask import Flask, jsonify
app = Flask(__name__)
@app.route('/')
def home():
return jsonify({"message": "Welcome to the Book API!"})
if __name__ == '__main__':
app.run(debug=True)
Run the app:
python app.py
Then open http://127.0.0.1:5000/
in your browser — you’ll see the welcome message.
📚 Step 4: Create a Sample Dataset
Add a simple list of books above your routes:
books = [
{"id": 1, "title": "The Pragmatic Programmer", "author": "Andrew Hunt"},
{"id": 2, "title": "Clean Code", "author": "Robert C. Martin"}
]
🧱 Step 5: Add CRUD Endpoints
✅ GET all books
@app.route('/api/books', methods=['GET'])
def get_books():
return jsonify(books)
✅ GET a single book by ID
@app.route('/api/books/<int:book_id>', methods=['GET'])
def get_book(book_id):
book = next((b for b in books if b["id"] == book_id), None)
if book:
return jsonify(book)
return jsonify({"error": "Book not found"}), 404
✅ POST (Create) a new book
from flask import request
@app.route('/api/books', methods=['POST'])
def add_book():
data = request.get_json()
new_book = {
"id": len(books) + 1,
"title": data.get("title"),
"author": data.get("author")
}
books.append(new_book)
return jsonify(new_book), 201
✅ PUT (Update) an existing book
@app.route('/api/books/<int:book_id>', methods=['PUT'])
def update_book(book_id):
data = request.get_json()
book = next((b for b in books if b["id"] == book_id), None)
if book is None:
return jsonify({"error": "Book not found"}), 404
book["title"] = data.get("title", book["title"])
book["author"] = data.get("author", book["author"])
return jsonify(book)
✅ DELETE a book
@app.route('/api/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"}), 200
🧩 Full app.py Example
Here’s the full working code:
from flask import Flask, jsonify, request
from flask_cors import CORS
app = Flask(__name__)
CORS(app)
books = [
{"id": 1, "title": "The Pragmatic Programmer", "author": "Andrew Hunt"},
{"id": 2, "title": "Clean Code", "author": "Robert C. Martin"}
]
@app.route('/')
def home():
return jsonify({"message": "Welcome to the Book API!"})
@app.route('/api/books', methods=['GET'])
def get_books():
return jsonify(books)
@app.route('/api/books/<int:book_id>', methods=['GET'])
def get_book(book_id):
book = next((b for b in books if b["id"] == book_id), None)
if book:
return jsonify(book)
return jsonify({"error": "Book not found"}), 404
@app.route('/api/books', methods=['POST'])
def add_book():
data = request.get_json()
new_book = {
"id": len(books) + 1,
"title": data.get("title"),
"author": data.get("author")
}
books.append(new_book)
return jsonify(new_book), 201
@app.route('/api/books/<int:book_id>', methods=['PUT'])
def update_book(book_id):
data = request.get_json()
book = next((b for b in books if b["id"] == book_id), None)
if not book:
return jsonify({"error": "Book not found"}), 404
book["title"] = data.get("title", book["title"])
book["author"] = data.get("author", book["author"])
return jsonify(book)
@app.route('/api/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"}), 200
if __name__ == '__main__':
app.run(debug=True)
🧪 Step 6: Test Your API
You can test your endpoints with:
✅ cURL
curl http://127.0.0.1:5000/api/books
✅ Postman or Thunder Client
GET → /api/books
POST → /api/books
{ "title": "Fluent Python", "author": "Luciano Ramalho" }
PUT → /api/books/1
{ "title": "Updated Title" }
DELETE → /api/books/2
🗄️ Step 7: (Optional) Connect to a Database
You can integrate Flask-SQLAlchemy to persist data.
Install:
pip install flask_sqlalchemy
Example setup:
from flask_sqlalchemy import SQLAlchemy
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///books.db'
db = SQLAlchemy(app)
class Book(db.Model):
id = db.Column(db.Integer, primary_key=True)
title = db.Column(db.String(120), nullable=False)
author = db.Column(db.String(120), nullable=False)
Run:
from app import db
db.create_all()
Now you can replace the list-based logic with database queries.
🔐 Step 8: Add Security & Best Practices
Security Feature Flask Extension Description
CORS flask-cors Allow cross-origin requests safely
Auth flask-jwt-extended Add JWT authentication
Validation marshmallow Validate request payloads
Rate limiting flask-limiter Prevent abuse and DDoS
Example JWT setup:
pip install flask-jwt-extended
☁️ Step 9: Deploy Your Flask API
You can deploy easily to:
Render, Railway, or Heroku
AWS, Azure, or Google Cloud
Using Docker:
FROM python:3.12
WORKDIR /app
COPY . .
RUN pip install -r requirements.txt
CMD ["python", "app.py"]
✅ Summary
Step Description
1️⃣ Install Flask and set up project
2️⃣ Create endpoints for CRUD operations
3️⃣ Use JSON for input/output
4️⃣ Test with Postman or curl
5️⃣ Add persistence with SQLAlchemy
6️⃣ Secure your API (CORS, JWT, etc.)
7️⃣ Deploy to the cloud
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