Python and REST APIs: Building, Testing, and Documenting

Introduction
Prerequisites
Setup
Building a REST API with Python
Testing a REST API
Documenting a REST API
Recap

Introduction

In this tutorial, we will learn how to build, test, and document a REST API using Python. A REST (Representational State Transfer) API is a popular architectural style for designing networked applications. We will cover the entire process from setting up our development environment to making requests and documenting our API.

By the end of this tutorial, you will be able to:

Build a RESTful API using Python and a web framework
Test your API using automated testing techniques
Document your API using a popular tool

Let’s get started!

Prerequisites

Before you start this tutorial, you should have a basic understanding of the Python programming language and web development concepts. Knowledge of HTTP protocol and JSON will also be beneficial.

Setup

To follow along with this tutorial, you need to have the following software installed on your machine:

Python 3: Visit the official Python website and download the latest version of Python 3 for your operating system. Follow the installation instructions provided.
Flask: Flask is a popular web framework for building REST APIs in Python. Open a terminal or command prompt and install Flask using the following command:
```
 pip install flask
```
Postman: Postman is a powerful API testing tool. Download and install Postman from the official website.

Now that we have our prerequisites in place, let’s move on to building our REST API.

Building a REST API with Python

Step 1: Set up a new Flask project

Create a new directory for your project and navigate to it using the terminal or command prompt.

Initialize a new Flask project by running the following command:

 mkdir my_api
 cd my_api
 python -m venv venv
 source venv/bin/activate  # For Mac/Linux
 venv\Scripts\activate  # For Windows

Create a new Python file called app.py in the project directory.
Open app.py in a text editor and import the Flask module:
```
 from flask import Flask
	
 app = Flask(__name__)
```
Step 2: Define API endpoints
In app.py, define your API endpoints using Flask’s @app.route decorator. For example, to create a simple “Hello, World!” endpoint, add the following code:
```
 @app.route('/')
 def hello_world():
     return 'Hello, World!'
```
Save the file and run the Flask development server:
```
 flask run
```
Open your web browser and visit http://localhost:5000 (or the URL provided by Flask) to see your “Hello, World!” message.

Congratulations! You have built your first REST API using Python and Flask.

Testing a REST API

Step 1: Install pytest

In your venv environment, install pytest using the following command:
```
 pip install pytest
```
Step 2: Write unit tests
Create a new directory called tests in your project directory.
Inside the tests directory, create a new file called test_api.py.
In test_api.py, import the necessary modules:
```
 import pytest
 from app import app
```

Write test functions to test your API endpoints. For example, to test the “Hello, World!” endpoint, add the following code:

 def test_hello_world():
     with app.test_client() as client:
         response = client.get('/')
         assert response.data == b'Hello, World!'
         assert response.status_code == 200

Step 3: Run tests

In your terminal or command prompt, navigate to the project directory.
Run the tests using the following command:
```
 pytest
```
Great job! You have successfully tested your REST API using pytest.

Documenting a REST API

Step 1: Install Swagger UI

In your venv environment, install flasgger using the following command:
```
 pip install flasgger
```
Step 2: Add Swagger annotations
Open app.py in a text editor.

Import the necessary modules:

 from flasgger import Swagger
	
 app = Flask(__name__)
 swagger = Swagger(app)

Add Swagger annotations to your API endpoints. For example, to document the “Hello, World!” endpoint, modify the code as follows:

 @app.route('/')
 def hello_world():
     """
     This is an example endpoint.
     ---
     responses:
       200:
         description: A simple 'Hello, World!' message.
     """
     return 'Hello, World!'

Step 3: Generate Swagger documentation

In your terminal or command prompt, navigate to the project directory.
Run the Flask development server:
```
 flask run
```
Open your web browser and visit http://localhost:5000/apidocs to see the Swagger documentation for your API.

Congratulations! You have successfully documented your REST API using Swagger.

Recap

In this tutorial, we learned how to build a REST API using Python and Flask, test it using pytest, and document it using Swagger. We covered the entire process from setup to implementation, testing, and documentation. Here are the key points to remember:

Use Flask to build your RESTful API.
Test your API using pytest and write unit tests for each endpoint.
Document your API using Swagger annotations and generate Swagger documentation.

By following these steps, you can create robust REST APIs with Python and ensure their functionality and accessibility.

Now it’s time to apply these concepts to your own projects and continue exploring the world of RESTful API development with Python!

Published: 25 May 2021