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 functionsfrom flask import Flask, jsonify, request # creating a Flask appapp = 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 functionif __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_restfulfrom flask import Flask, jsonify, requestfrom flask_restful import Resource, Api # creating the flask appapp = Flask(__name__)# creating an API objectapi = 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 numberclass Square(Resource): def get(self, num): return jsonify({'square': num**2}) # adding the defined resources along with their corresponding urlsapi.add_resource(Hello, '/')api.add_resource(Square, '/square/<int:num>') # driver functionif __name__ == '__main__': app.run(debug = True) |
Output:
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