Python | Build a REST API using Flask (original) (raw)

Last Updated : 25 Feb, 2022

Prerequisite: Introduction to Rest APIREST stands for REpresentational State Transfer and is an architectural style used in modern web development. It defines a set or rules/constraints for a web application to send and receive data. In this article, we will build a REST API in Python using the Flask framework. Flask is a popular micro framework for building web applications. Since it is a micro-framework, it is very easy to use and lacks most of the advanced functionality which is found in a full-fledged framework. Therefore, building a REST API in Flask is very simple. There are two ways of creating a REST API in Flask:

Using Flask without any external libraries
Using flask_restful library

Libraries required:

flask_restful can be installed via the pip command:

 sudo pip3 install flask-restful

Method 1: using only Flask

Here, there are two functions: One function to just return or print the data sent through GET or POST and another function to calculate the square of a number sent through GET request and print it.

python3 1== `

Using flask to make an api

import necessary libraries and functions

from flask import Flask, jsonify, request

creating a Flask app

app = Flask(name)

on the terminal type: curl http://127.0.0.1:5000/

returns hello world when we use GET.

returns the data that we send when we use POST.

@app.route('/', methods = ['GET', 'POST']) def home(): if(request.method == 'GET'):

    data = "hello world"
    return jsonify({'data': data})

A simple function to calculate the square of a number

the number to be squared is sent in the URL when we use GET

on the terminal type: curl http://127.0.0.1:5000 / home / 10

this returns 100 (square of 10)

@app.route('/home/int:num', methods = ['GET']) def disp(num):

return jsonify({'data': num**2})

driver function

if name == 'main':

app.run(debug = True)

Output: Executing the square function:

Method 2: Using flask-restful

Flask Restful is an extension for Flask that adds support for building REST APIs in Python using Flask as the back-end. It encourages best practices and is very easy to set up. Flask restful is very easy to pick up if you're already familiar with flask. In flask_restful, the main building block is a resource. Each resource can have several methods associated with it such as GET, POST, PUT, DELETE, etc. for example, there could be a resource that calculates the square of a number whenever a get request is sent to it. Each resource is a class that inherits from the Resource class of flask_restful. Once the resource is created and defined, we can add our custom resource to the api and specify a URL path for that corresponding resource.

python3 1== `

using flask_restful

from flask import Flask, jsonify, request from flask_restful import Resource, Api

creating the flask app

app = Flask(name)

creating an API object

api = Api(app)

making a class for a particular resource

the get, post methods correspond to get and post requests

they are automatically mapped by flask_restful.

other methods include put, delete, etc.

class Hello(Resource):

# corresponds to the GET request.
# this function is called whenever there
# is a GET request for this resource
def get(self):

    return jsonify({'message': 'hello world'})

# Corresponds to POST request
def post(self):
    
    data = request.get_json()     # status code
    return jsonify({'data': data}), 201

another resource to calculate the square of a number

class Square(Resource):

def get(self, num):

    return jsonify({'square': num**2})

adding the defined resources along with their corresponding urls

api.add_resource(Hello, '/') api.add_resource(Square, '/square/int:num')

driver function

if name == 'main':

app.run(debug = True)

Output: