Introduction to REST API in Python

 

APIs are the backbone of modern web development, allowing systems to communicate and exchange data. If you're working with Python, building a REST API in Python is one of the most practical skills you can learn—whether you're building web apps, microservices, or mobile backends.

This article introduces the core concepts of REST APIs, explains why Python is ideal for API development, and shows how to get started with a real-world example.

What Is a REST API?

REST (Representational State Transfer) is an architectural style that uses HTTP methods (GET, POST, PUT, DELETE) to interact with resources. RESTful APIs are stateless, meaning each request from the client must contain all the information needed to process it.

Key principles of REST APIs:

• Stateless communication

• Resource-based (usually in JSON)

• Use of standard HTTP methods

• Uniform interface and consistent URLs

Example:

bash
GET /users/123  
POST /users  
DELETE /users/123  

Why Use Python for REST APIs?

Python is widely used in backend development thanks to:

• Simple, readable syntax

• Powerful libraries and frameworks (Flask, FastAPI, Django)

• Large developer community and ecosystem

• Great for prototyping and production

Whether you're building a basic API or a scalable service, Python makes it fast and easy.

Build a Simple REST API Using Flask

Flask is a lightweight Python framework perfect for creating small, fast APIs.

Step 1: Install Flask

bash
pip install Flask

Step 2: Create a Basic API

python
from flask import Flask, jsonify, request

app = Flask(__name__)

users = [{"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"}]

@app.route('/users', methods=['GET'])
def get_users():
    return jsonify(users)

@app.route('/users/<int:user_id>', methods=['GET'])
def get_user(user_id):
    user = next((u for u in users if u["id"] == user_id), None)
    return jsonify(user) if user else ("User not found", 404)

@app.route('/users', methods=['POST'])
def create_user():
    data = request.get_json()
    new_user = {"id": len(users) + 1, "name": data["name"]}
    users.append(new_user)
    return jsonify(new_user), 201

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

You now have a basic REST API that supports GET and POST.

Alternative Frameworks

• FastAPI – High-performance, modern Python framework with async support and automatic documentation.

• Django REST Framework – Great for complex apps with built-in admin and ORM.

• Tornado / Sanic – For high-performance, asynchronous use cases.

Best Practices

• Use meaningful endpoints (/users, /posts, /products)

• Follow HTTP status codes correctly (200, 201, 400, 404, 500)

• Secure APIs with authentication (API keys, OAuth)

• Use versioning (/api/v1/users)

• Write automated tests for endpoints

Related Reads

• What is Unit Testing

• Python Code for Pulling API Data

• What Does Enumerate Do in Python

Conclusion

Learning how to build a REST API in Python is a powerful skill that can open the door to countless projects, from web apps to automation scripts. Whether you start with Flask or FastAPI, Python makes building and maintaining APIs simple and scalable.

Looking to automate API testing? Try Keploy — an open-source tool that records real traffic and auto-generates test cases and mocks, perfect for streamlining your API development workflow.