Hello World Flask Application

What is a Flask

Flask is a microframework for Python. It is a thin layer on top of the standard Python Web Server, WSGI, and the web application itself. Flask is designed to make it easy to create small web applications. Check out the Flask Documentation.

Flask Installation using pip

python3 is required.

pip install flask

If you already have flask installed, make sure you have the latest version.

pip install --upgrade flask

Create you flask app

Open a new terminal window and navigate to the directory where you want to create your flask app. You can create a new directory with the following command:

mkdir flask_app
cd flask_app

Now create a new file called app.py and paste the following code into it:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def index():
    return "Hello World!"


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

In the terminal, run the following command to run the app:

python app.py

You should see the following output:

 * Serving Flask app "app" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

Copy the url(http://127.0.0.1:5000/) from the output and paste it into your browser. You should see the following output:

Voila! You have created a simple flask app.