Building Your First Web API with Flask

Flask is a lightweight and powerful web framework for Python that makes it easy to build web APIs. In this tutorial, we'll create a simple but complete REST API.

Setting Up Flask

First, let's install Flask and set up our basic application structure:

pip install flask

Creating Your First API

Here's how to create a basic Flask API:

from flask import Flask, jsonify, request

app = Flask(__name__)

# Sample data
books = [
    {"id": 1, "title": "Python Crash Course", "author": "Eric Matthes"},
    {"id": 2, "title": "Automate the Boring Stuff", "author": "Al Sweigart"}
]

@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((book for book in books if book["id"] == book_id), None)
    if book:
        return jsonify(book)
    return jsonify({"error": "Book not found"}), 404

@app.route('/api/books', methods=['POST'])
def create_book():
    data = request.get_json()
    new_book = {
        "id": len(books) + 1,
        "title": data["title"],
        "author": data["author"]
    }
    books.append(new_book)
    return jsonify(new_book), 201

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

API Endpoints

Our API now supports:

• GET /api/books - Get all books
• GET /api/books/:id - Get a specific book
• POST /api/books - Create a new book

Testing Your API

You can test your API using curl or Postman:

# Get all books
curl http://localhost:5000/api/books

# Get a specific book
curl http://localhost:5000/api/books/1

# Create a new book
curl -X POST http://localhost:5000/api/books \
  -H "Content-Type: application/json" \
  -d '{"title": "Learning Python", "author": "Mark Lutz"}'

Next Steps

This is just the beginning! In future tutorials, we'll cover:

• Database integration with SQLAlchemy
• Authentication and authorization
• API documentation with Swagger
• Deployment to production

Flask makes it easy to start building APIs, and with these foundations, you're ready to create more complex applications.