Adventures in Machine Learning

Building a REST API with Flask: A Beginner’s Guide

Introduction to APIs and REST APIs

In today’s world, almost all software applications interact with each other through APIs. Whether it’s your smartphone’s weather app or the payment gateway for your online shopping, APIs make it possible for these applications to communicate with each other.

API Interaction between Applications

APIs (Application Programming Interfaces) are sets of protocols, standards, and tools used to build software applications. APIs provide a way for developers to interact and communicate with other software applications, platforms, and web services.

In simpler terms, APIs are like a waiter in a restaurant. The waiter takes your order and passes it on to the kitchen.

The kitchen prepares the food and hands it back to the waiter, who then delivers it to you. The same concept applies to APIs. When you interact with an API, you make a request, which is then handled by the API server, and you get a response back.

CRUD Operators and HTTP Methods

APIs usually expose CRUD (Create, Read, Update, Delete) operations through HTTP (Hypertext Transfer Protocol) methods. HTTP methods include GET, PUT, POST, and DELETE, which are used to request, update, post, and delete data, respectively.

For instance, a GET request would be used to retrieve data, while a POST request would be used to submit data to a server. Similarly, a PUT request is used to update existing data, and a DELETE request is used to remove existing data.

What is a REST API? Rest API (Representational State Transfer API) is a type of API that uses the HTTP protocol to access web services.

In a REST API, resources are identified with unique URLs, which can be accessed using HTTP methods.

Resources can be anything from data to images or even web pages.

For example, if you want to access a specific resource on a website, you can make a request using an API, and the server will send back the requested resource.

Statelessness of Rest APIs

A significant feature of REST APIs is that they are stateless, meaning there is no prior context or history maintained between requests. Each request is treated independently, which makes REST APIs much more scalable than other types of APIs.

For instance, let’s say you want to access a website’s catalog through its REST API.

You would make a request for the catalog, and the server would return the necessary data. The next time you want to request something from the catalog, you would have to make another separate request.

The API server does not keep track of your previous requests, so the next request is treated like a fresh request.

Installing Postman

Postman is an API development environment that allows developers to create, manage, and test APIs. It provides a user-friendly platform to make API requests and test their responses.

Function and Features of Postman

Postman offers several features that make it an essential tool for API development. Some of these features include:

1.

User-Friendly Interface: Postman provides a clean and user-friendly interface that makes it easy to work with APIs.

2. API Documentation: Postman allows developers to document their APIs, making it easier for others to understand and work with the APIs.

3.

API Testing: Postman allows developers to test APIs and ensure that they are working correctly.

4.

Collaboration: Postman provides a platform for team collaboration, allowing multiple users to work on the same API project.

How to Install Postman

Postman is available for download on Windows, Mac, and Linux. Follow these steps to install Postman:

1.

Go to the Postman website (www.postman.com) and click on the “Download” button.

2.

Select your operating system to start the download.

3.

Once the download is complete, open the downloaded file to start the installation process.

4.

Follow the installation wizard to complete the installation.

Conclusion

In conclusion, APIs and REST APIs are essential components of modern software development. They enable communication and interaction between different software applications and platforms.

REST APIs, in particular, are widely used because they are scalable and stateless.

Postman is a vital tool for API development that allows developers to create, manage, and test their APIs. Its user-friendly interface and collaboration features make it an ideal platform for teams working on API development.

With the information provided in this article, you can now create and manage your APIs using Postman.

Building a Flask REST API Application

Flask is a lightweight and flexible framework for building web applications and REST APIs. Flask can be integrated with a variety of databases, including SQLite, MySQL, and PostgreSQL. This article will guide you through building a REST API application using Flask, SQLite, and SQLAlchemy.

Installing Flask_restful

Flask_restful is a Flask extension for building RESTful APIs. It provides an easy-to-use interface for handling requests and managing resources. To install Flask_restful, open your command prompt and type the following command:

“`

pip install flask-restful

“`

This command will install Flask_restful and its dependencies.

Coding the DB Models using SQLAlchemy

SQLAlchemy is a Python library used for working with SQL databases. It provides a set of tools for working with database models, managing database connections, and monitoring database activities.

To use SQLAlchemy with Flask, you need to install the following package:

“`

pip install flask-sqlalchemy

“`

Next, add the following code to your application file to create the database model:

“`python

from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)

app.config[‘SQLALCHEMY_DATABASE_URI’] = ‘sqlite:////tmp/test.db’

db = SQLAlchemy(app)

class Book(db.Model):

id = db.Column(db.Integer, primary_key=True)

title = db.Column(db.String(80), nullable=False)

author = db.Column(db.String(120), nullable=False)

“`

This code creates a Book model with id, title, and author attributes.

Coding the Flask Application

Next, create a Flask application using the following code:

“`python

from flask import Flask

from flask_restful import Api

app = Flask(__name__)

api = Api(app)

“`

This code creates a Flask application and an instance of the Api class to handle API requests.

Adding a Books List Resource

To create a books list resource, add the following code:

“`python

from flask_restful import Resource

class BooksList(Resource):

def get(self):

pass

def post(self):

pass

api.add_resource(BooksList, ‘/books’)

“`

This code creates a BooksList class that handles GET and POST requests for /books.

Adding a Book Resource

Next, create a Book resource using the following code:

“`python

class Book(Resource):

def get(self, id):

pass

def put(self, id):

pass

def delete(self, id):

pass

api.add_resource(Book, ‘/books/‘)

“`

This code creates a Book class that handles GET, PUT, and DELETE requests for /books/.

Implementing the Flask REST API application using POSTMAN

Now that we have our Flask REST API application set up, we can test it using POSTMAN. Below are some examples of how to use POSTMAN to interact with the application.

Creating a Book Resource Using POST Method

To create a new book resource using the POST method, open POSTMAN and create a new POST request to the /books endpoint. In the body section of the request, enter the title and author of the book as JSON data.

Click on the Send button to submit the request. “`

POST /books HTTP/1.1

Host: 127.0.0.1:5000

Content-Type: application/json

Cache-Control: no-cache

{

“title”: “Flask RESTful API”,

“author”: “John Doe”

}

“`

BooksList Resource: POST Method

To add a new book using POST method on BooksList Resource, create a new POST request to the /books endpoint.

In the body section of the request, enter the title and author of the book as JSON data. “` python

def post(self):

args = parser.parse_args()

book = Book()

book.title = args[‘title’]

book.author = args[‘author’]

db.session.add(book)

db.session.commit()

return {‘message’: ‘Book added successfully’, ‘data’: {

‘id’: book.id,

‘title’: args[‘title’],

‘author’: args[‘author’]

}}, 201

“`

Book Resource: GET Method

To retrieve the details of a book resource using the GET method, create a new GET request to the /books/id endpoint, where id is the id of the book.

“`python

def get(self, id):

book = Book.query.filter_by(id=id).first()

if not book:

return {‘message’: ‘Book not found’}, 404

return {‘id’: book.id, ‘title’: book.title, ‘author’: book.author}, 200

“`

Book Resource: PUT Method

To update a book resource using the PUT method, create a new PUT request to the /books/id endpoint, where id is the id of the book. In the body section of the request, enter the updated title and author of the book as JSON data.

“`python

def put(self, id):

book = Book.query.filter_by(id=id).first()

if not book:

return {‘message’: ‘Book not found’}, 404

args = parser.parse_args()

book.title = args[‘title’]

book.author = args[‘author’]

db.session.add(book)

db.session.commit()

return {‘message’: ‘Book updated successfully’, ‘data’: {

‘id’: book.id,

‘title’: args[‘title’],

‘author’: args[‘author’]

}}, 200

“`

Book Resource: DELETE Method

To delete a book resource using the DELETE method, create a new DELETE request to the /books/id endpoint, where id is the id of the book. “`python

def delete(self, id):

book = Book.query.filter_by(id=id).first()

if not book:

return {‘message’: ‘Book not found’}, 404

db.session.delete(book)

db.session.commit()

return {‘message’: ‘Book deleted successfully’}, 200

“`

Conclusion

In this article, we have explored the process of building a REST API application using the Flask framework and a SQLite database. We have also covered the basic implementations of RESTful CRUD operations using Flask_restful and explained how to use POSTMAN to test these implementations.

By following the steps outlined in this article, you can create your own REST API using Flask and easily scale your application as per your requirements.

Conclusion:

In this article, we have covered the basics of building a REST API using Flask in Python. We first learned about APIs and their importance for modern software development.

Then, we discussed what a REST API is, their properties, and how they work. We also looked at the importance of APIs in allowing different applications to communicate with each other.

We then covered the installation of Flask_restful and SQLAlchemy libraries. These libraries are essential for building REST APIs with Flask.

We also created the necessary database models and created the Flask application. We then implemented two different resource handlers for our application, one for handling a list of books and the other for handling individual books.

Finally, we demonstrated how to use POSTMAN, a widely used tool for testing REST APIs, to test our application by implementing different HTTP methods like GET, POST, PUT, and DELETE. We performed these operations on the resources we created namely ‘Books list resource’ and ‘Book resource’.

By following the guidelines outlined in this article, you can create a simple but effective REST API using Flask, which can be expanded and scaled as per your requirements. It is worth noting that while we have covered the basics of building REST APIs using Flask, there is still much more to learn, and the field is continually evolving.

However, this article provides a good starting point for those looking to build REST APIs using Flask. In conclusion, REST APIs offer a lot of benefits for software developers and their users.

They allow for a standardized way of accessing resources and enable different platforms to communicate with each other. Flask, with its straightforward and flexible nature, is an excellent choice for building REST APIs. With Flask, you can build APIs that are easy to maintain, scalable, and can provide significant benefits to your software development projects.

In summary, this article has introduced the concepts of APIs and REST APIs, which are essential components of modern software development that allow different applications to communicate and interact with each other. We have covered the basics of building a REST API using Flask in Python, including installing the required libraries, coding the Flask application, and testing it using POSTMAN.

The article provides a good starting point for those looking to build REST APIs using Flask. By creating a REST API using Flask, you can build scalable, maintainable APIs that provide significant benefits to software development projects.

Overall, this article emphasizes the importance of understanding REST APIs and its role in modern software development.