How to send JSON data in python flask

ByJerry Richard R

Flask is a well-known web application micro-framework written in Python using which developers can create web applications easily and efficiently. It provides a flexible, lightweight, and simple structure for creating the REST API. REST (Representational State Transfer) API is used to set guidelines for a web application to send and receive information. It can be used to exchange information between the client and server. 

This article will provide a step-by-step guide on how to Send JSON Data in Python Flask, demonstrating how to create a simple REST API that returns a JSON object using Flask. This makes it an ideal resource for developers who want to learn about REST API development.

Install Required Modules:

First, let’s download the required Python libraries:

  • Run this command to install Flask Library:
pip install Flask
  • Run this command to install Flask-RESTful Library:
pip install Flask-RESTful

Return a JSON Response

There are different ways to return a JSON response from a Flask API. Some of them are discussed below:

  1. Using jsonify Method
  2. Using flask_restful Library 

Using jsonify Method

To send JSON data in python using flask:

  • Use the jsonify method available in the FLASK library. This method is used to return JSON output in a Response object. Let’s see the below example that shows how to send JSON data in python flask:
#Load libraries
from flask import Flask,request,jsonify
​
# A Flask app instance
app = Flask(__name__)
​
# route the app to the given URL
@app.route('/api/example' , methods = ['GET'])
​
​
# Define app
def example_api():
if(request.method == 'GET'):
data={
"Name": "Hi! Burhan",
"Age" : 25,
"Message": "Congratulations! You have successfully return a JSON response from a Flask API",
}
return jsonify(data)
​
# build the Flask app
if __name__ == '__main__':
  app.run()    

Save the above code as myApp.py and run it on the command prompt or any python IDE using the following command :

python myApp.py

You can also use the below command on the command prompt to run the myApp.py file

flask --app myApp run

Output

This code is a simple Flask application that returns a JSON response when a GET request is made to the endpoint /api/example. Here’s a step-by-step explanation:

  • At first, the jsonify and all required methods are imported from the flask framework.
  • A Flask app instance is created using the Flask constructor.
  • The app is then routed to the endpoint /api/example using the @app.route method.
  • Then example_api function is created. The get method is implemented in the example_api to handle a GET request to the endpoint. In the function, a dictionary is created with some data and the jsonify method is used to convert it to a JSON response, which is returned to the client. 
  • Finally, the Flask app is run in the if __name__ == ‘__main__’ block, making it ready to receive and respond to requests.

Using flask_restful Library 

To send JSON data in python using flask:

  • Flask-RESTful library can also be used. Flask-RESTful is an extension for Flask that adds support for building REST APIs. Consider the below example of using Flask-RESTful to return a JSON response from a Flask API:
from flask import Flask
from flask_restful import Api, Resource
​
app = Flask(__name__)
​
api = Api(app)
​
class ExampleAPI(Resource):
def get(self):
data={

"Name": "Hi! Burhan",
"Age" : 25,
"Message": "Congratulations! You have successfully return a JSON response from a Flask API",
}
return data
​
api.add_resource(ExampleAPI,'/api/example2')
​
​
if __name__=='__main__':
app.run(debug=True)
​

Save the above code as myApp2.py and run it on the command prompt or any python IDE using the following command :

python myApp2.py
# flask --app myApp2 run

Output

The above example demonstrates how to send JSON data in python Flask using flask_restful Library. An explanation of the above code is given below:

  • Load the jsonify method from the flask framework and Api and Resource methods are imported from flask_restful library.
  • A Flask app instance is then created using the Flask constructor.
  • An instance of the Flask-RESTful Api class is created, passing the Flask app instance as an argument.
  • The Resource class named ExampleAPI is defined, which handled the endpoint for the API.
  • The get method is implemented in the ExampleAPI class to handle a GET request. This method returned a dictionary that was converted to a JSON response.
  • The add_resource method is called on the Flask-RESTful API instance, passing the ExampleAPI class and the response path /api/example2 as arguments.
  • Then if __name__ == ‘__main__’ block is used to run the Flask app in debug mode, which allows for easy debugging during development.

When a GET request is made to the /api/example2 endpoint, the get method in the ExampleAPI class is called, which returns a dictionary representing the JSON response. Flask-RESTful automatically converts this dictionary to a JSON response and sends it back to the client.

Conclusion:

A REST API, or Representational State Transfer API, defines a set of rules and constraints for designing and building web applications that communicate and exchange data over the internet. In simple terms, a REST API acts as a bridge between different components of an application and enables them to send and receive data in a structured manner.

In the context of this article, we specifically showed how to create a REST API that returns a simple JSON object in Python using the Flask framework. We utilized the jsonify method and the flask_restful library to achieve this. By leveraging these tools, we demonstrated how to send JSON data in Python flask in a clear and organized format, making it easier for different parts of the application to communicate and exchange information.

Check here for more python articles

Good Luck with your Learning !!

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