Developing a Flask Web App from the Ground Up: A Comprehensive Guide

Flask is a lightweight Python web framework that provides useful tools and features for creating web applications. In this tutorial, we will go through the process of creating a simple Flask application from scratch.


Before we get started, make sure you have the following tools installed on your computer:

  • Python 3.6 or higher
  • Pip, the Python package manager

Step 1: Set up a Python Virtual Environment

It is generally a good idea to set up a Python virtual environment before installing any Python packages. This will allow you to isolate the packages you install for this project from the packages installed on your system.

To set up a virtual environment, open a terminal and navigate to the directory where you want to create your project. Then, run the following command:

python -m venv env

This will create a new directory called “env” that contains a Python virtual environment. To activate the virtual environment, run the following command:

source env/bin/activate

Your virtual environment should now be activated, as indicated by the “(env)” prefix in the terminal prompt.

Step 2: Install Flask

Now that we have our virtual environment set up, we can install Flask using pip. Run the following command to install Flask:

pip install Flask

This will install Flask and all of its dependencies.

Step 3: Create a Flask Application

Now that we have Flask installed, we can create our Flask application. Create a new file called “” and add the following code:

from flask import Flask

app = Flask(__name__)

def hello():
    return 'Hello, World!'

if __name__ == '__main__':

This code creates a new Flask application and defines a single route, ‘/’, that returns the text “Hello, World!”.

Step 4: Run the Application

To run the application, open a terminal and navigate to the directory where your “” file is located. Then, run the following command:

flask run

This will start the Flask development server, which will host your application at http://localhost:5000. Open a web browser and navigate to that URL to see your application in action.

Step 5: Customize the Application

Now that you have a basic Flask application up and running, you can start customizing it to your liking. Here are a few things you can do to take your application to the next level:

  • Define additional routes and functions to handle different URL paths
  • Use templates to create dynamic HTML pages
  • Use a database to store and retrieve data
  • Use Flask extensions to add additional functionality, such as user authentication or form validation


In this tutorial, we have seen how to create a simple Flask application from scratch. Flask is a powerful and flexible web framework that provides a variety of tools and features for building web applications. With a little bit of Python knowledge and some creativity, you can use Flask to build just about anything.

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