A Beginner’s Guide to Creating Simple Web Applications

This tutorial will guide you through the process of building a simple web application using Python, Flask, and HTML. You’ll learn about the core components, how they work together, and practical steps …

Updated August 26, 2023

Welcome to the exciting world of web development! This tutorial introduces you to building basic web applications using Python. We’ll be using the Flask framework – a lightweight and powerful tool that makes creating web apps accessible and fun.

What is a Web Application?

Think of websites like Facebook, Twitter, or online stores – these are all examples of web applications. They allow users to interact with data, perform actions, and receive dynamic content over the internet.

Here’s how it works:

Request: When you visit a website in your browser, you send a request to a server asking for specific information (like a webpage).
Processing: The server receives your request, processes it, often using code written in languages like Python, and retrieves the necessary data.
Response: The server sends back a response, which is typically formatted as HTML (the language that structures webpages) along with CSS for styling and JavaScript for interactive elements. Your browser then renders this information, displaying the website you see.

Why Python for Web Development?

Python is an excellent choice for web development due to its:

Simplicity and Readability: Python’s clear syntax makes it easy to learn and understand, even for beginners.
Extensive Libraries: Python has a rich ecosystem of libraries (pre-written code modules) specifically designed for web development, like Flask and Django.
Large Community: A vast community of Python developers means abundant support, resources, and solutions are readily available online.

Introducing Flask: Your Web Framework

Flask is a micro-framework for Python that provides the essential tools to build web applications without unnecessary complexities. Think of it as the foundation on which you’ll construct your website.

Key Features:

Routing: Flask handles directing requests from users (like visiting a specific URL) to the correct parts of your code.
Templating: It allows you to create dynamic HTML pages by inserting Python variables and logic into templates.

Building Our First Web App: A “Hello World” Example

Let’s dive into creating a simple web app that displays “Hello, world!” when accessed in a browser.

Step 1: Setting Up

Make sure you have Python installed on your system. You can download it from https://www.python.org/. Then, use pip (Python’s package manager) to install Flask:

pip install flask

Step 2: Creating the App Code

Create a new Python file named app.py. Inside this file, paste the following code:

from flask import Flask, render_template

app = Flask(__name__)

@app.route('/')
def hello():
    return "Hello, world!"

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

Let’s break down this code:

from flask import Flask, render_template: We import the necessary components from the Flask library.
app = Flask(__name__): This creates an instance of our Flask application.
@app.route('/'): This decorator tells Flask to associate the hello() function with the root URL ("/"). When a user visits your app’s homepage, this function will be executed.
def hello():: Defines the hello() function that simply returns the text “Hello, world!”.
if __name__ == '__main__':: This block ensures the app runs only when executed directly (not imported as a module).
app.run(debug=True): Starts the development server with debugging enabled.

Step 3: Running Your App

Open your terminal or command prompt and navigate to the directory containing app.py. Run the following command:

python app.py

You’ll see output similar to this, indicating that the server is running:

 * 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: on
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

Open your web browser and go to http://127.0.0.1:5000/. You should see “Hello, world!” displayed on the page. Congratulations – you’ve built your first web application!

Next Steps:

This is just a starting point! Flask allows you to build much more complex applications by incorporating HTML templates, handling user input (forms), interacting with databases, and using various extensions for added functionality.