Hello World Basic Flask App

PURPOSE

To start hosting your Python Apps on a Webserver, you would first need to deploy it locally.

The starting point of any such project, is to create a basic web server, and host your app on your machine's localhost (127.0.0.1).

This article is intended to be a Hello World project for such a use case

The Author assumes that you have some basic understanding of working with Python 3.

Step 0: [Optional] Creating a virtual environment

If you're on Windows, open command prompt and type:

py -m venv first_flask_app
cd first_flask_app/Scripts
./activate

Step 1: INITIAL SETUP

Installing Flask framework using pip

# inside the venv
pip install flask
# if you have skipped the step of creating a virtual environment
py -m pip install flask

Create a new project directory, and open a file named app.py inside it.

md Hello-World-Flask
cd Hello-World-Flask
gvim app.py

Step 2: CODING YOUR FIRST FLASK APP

Add the following to the app.py file:

from flask import Flask # importing the Flask module from the framework.

app = Flask(__name__) # initializing an app

if __name__ == "__main__":
  app.run(debug=True) # running the server when the file is called directly.

Run the app.py file.

py app.py

• Your command prompt will be telling you that a server is up and running on port 5000

Let's Serve our First Web Page.

Modify your app.py file like so:

from flask import Flask

app = Flask(__name__)

# Adding your first endpoint
# the @decorator app.route can take multiple arguments.
# for now, we will just past the path at which we want to serve our page.
@app.route('/') # serving at localhost:5000/ (localhost:5000)
def index():
  # whenever we visit the endpoint, `index` function will be called.
  return 'Hello World!' # just returning a plain string for now.

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

• That's about it, just visit localhost:5000 on your browser

Hello World!

• And bask in the glory of your simple yet powerful creation.

Next Blog: How to Serve HTML Pages using Flask