Building and Using RESTful APIs with Python

Hello everyone, I am Xiao Ai! Today we are going to explore a super useful skill in Python – RESTful API. Simply put, an API acts like a “microphone” between two programs, and a RESTful API is a particularly popular way of communicating. By mastering this, you can enable different programs to exchange data!

Sounds cool, right? Don’t worry, Xiao Ai will guide you step by step in the simplest way to master the use and creation of APIs. By the end of today’s content, you will be able to call APIs to retrieve data and even set up a simple API service!

1. What is an API?

API (Application Programming Interface) is the “bridge” between applications, defining how programs communicate with each other. A RESTful API is a special design style that:

Uses HTTP protocol for communication
Is centered around resources (like users, products)
Operates on resources through HTTP methods (GET, POST, etc.)

Imagine an API as a restaurant waiter: you (the client) tell the waiter (the API) what you want, and the waiter goes to the kitchen (the server) to bring you the food (data)~

2. Calling an API with Python

Let’s start with the simplest example: using Python to request data from a public weather API.

1. Install the requests library

pip install requests

2. Call the weather API

import requests

# Call the free weather API
response = requests.get('https://api.openweathermap.org/data/2.5/weather?q=Beijing&amp;appid=your_API_key')

# Check the returned data
print(response.status_code)  # Status code, 200 means success
print(response.json())      # Returned JSON data

Code Explanation:

requests.get(): Sends a GET request
response.json(): Converts the returned data into a Python dictionary

Tips:

You need to register at OpenWeatherMap to get a free API key
Remember to replace your_API_key in the code with your actual key

3. Understanding HTTP Methods

RESTful APIs use different HTTP methods to operate on resources:

Method	Purpose	Example
GET	Retrieve resources	Get user information
POST	Create resources	Create a new user
PUT	Update entire resources	Update all user information
PATCH	Update partial resources	Only update user phone number
DELETE	Delete resources	Delete a user

4. Creating a Simple API with Flask

Now let’s create our own API service using Python’s Flask framework!

1. Install Flask

pip install flask

2. Create the API service

Create a new app.py file:

from flask import Flask, jsonify, request

app = Flask(__name__)

# Simulate some data
books = [
    {"id": 1, "title": "Introduction to Python", "author": "Xiao Ai"},
    {"id": 2, "title": "Flask Guide", "author": "Reverse Love"}
]

# Get all books (GET /books)
@app.route('/books', methods=['GET'])
def get_books():
    return jsonify(books)

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

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

3. Run and Test the API

python app.py

Then test your API using Postman or curl:

GET http://127.0.0.1:5000/books to get all books
POST http://127.0.0.1:5000/books to add a new book

5. Handling API Errors

A good API should handle errors properly:

# Get specific book (GET /books/&lt;id&gt;)
@app.route('/books/&lt;int:book_id&gt;', 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

Code Explanation:

If the book is found, return the book information
If not found, return a 404 error and a message

6. Practical Application Scenarios

Once you learn about APIs, you can:

Develop backend services for mobile apps
Create systems with microservices architecture
Integrate third-party services (payments, maps, etc.)
Build web applications with separated front and back ends

Considerations:

In production environments, consider authentication (like JWT)
Important APIs should have access restrictions
The format of returned data should be uniformly standardized

Conclusion

Today we learned:✅ What RESTful APIs are and their uses✅ How to use Python to call third-party APIs✅ The different roles of HTTP methods✅ How to create your own API service with Flask✅ Basic error handling methods

Students, that’s all for today’s Python learning journey! Did you learn something? Try creating an API to manage movie information, and feel free to ask Xiao Ai in the comments if you have any questions. Happy learning!

Mini Exercise:

Extend the book API to add PUT and DELETE methods
Try calling a free news API to retrieve data