Prerequisite: Introduction to Rest API
REST 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.
# 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.
# 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: