The Flask Mega-Tutorial, Part I: Hello, World

Part I of the 2024 Flask Mega-Tutorial walks through the very first steps to get a Flask web application running locally and serves as the foundation for a 23‑chapter course. It points to GitHub-hosted example code (with browse/zip/diff links for each chapter) and encourages typing examples to learn. The chapter covers installing Python if needed, verifying the interpreter, and the recommended workflow of using per-project virtual environments to avoid dependency conflicts. It explains why pip should be used inside a venv, how to create and activate a virtual environment across Linux/Mac/Windows/PowerShell, and how to install Flask (defaulting to the latest 3.x while giving commands to stay on 2.x if desired). A quick check with import flask confirms installation.

The chapter then builds a minimal but structured “hello world” application: create a microblog project directory, add an app package, and write an __init__.py that instantiates the Flask application with app = Flask(__name__) and imports routes. It explains the distinction between the app package (the directory) and the app Flask instance (the variable), and notes that using __name__ helps Flask locate resources like templates. These steps provide a practical, reproducible starting point for following the rest of the tutorial series.