Flask API Tutorial - How to Create a Simple API in 4 Steps

In this short article, I want to demonstrate how to write the simplest API python code by using Flask microframework. I will walk you through it step by step to create a basic API that responds with a JSON message.

Step 1

Make sure you have install flask library, by issuing this command on your terminal

flask --version

in my case, i got replied Python 3.10.9, Flask 2.2.3, Werkzeug 2.2.3 but if not, then

pip install Flask

Step 2

Alright, now we're gonna whip up a basic Flask API:

• create a app.py file. put it on the root folder.
• need to import libaries, i.e Flask, jsonify

from flask import Flask, jsonify

app = Flask(__name__)

Step 3

We need to tell explicitly the route that will return the json response. So, we need to create an endpoint at the root URL or "/" that returns a message like the code below

@app.route("/")
def hello_world():
    message = {"message": "Hello, This message is your api response!"}
    return jsonify(message)

Step 4

Finally, we need to make our Flask app executable by putting

if __name__ == "__main__":
    app.run(debug=True)

code to the bottom of the app.py file to start the development server: In the end, the app.py code should look like this:

from flask import Flask, jsonify

app = Flask(__name__)

@app.route("/")
def hello_world():
    message = {"message": "Hello, This message is your api response!"}
    return jsonify(message)

if __name__ == "__main__":
    app.run(debug=True)

Save the file and open a terminal. Navigate to the directory where app.py is located and run the application:

python app.py

Great! You've created a simple Flask API that responds with a JSON message. You can extend this example by adding more routes and functionality as needed for your application.