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Lecture 2 Hello Flask
Tirsvad edited this page 2026-11-06 06:13:56 +01:00
Table of Contents

Lecture 2: The first Flask server

English · Dansk · Bahasa Malaysia

Lecture 2: The first Flask server

What the lecture covers

A library is called by your code, but a framework calls your code and decides the structure. The lecture creates the smallest Flask application in a file named hello.py (never flask.py, which would hide the library), installs Flask with pip, points FLASK_APP at the file and starts the server with flask run. The browser then shows "Hello, World!" from the local address. Ctrl+C stops the server so that two applications do not fight over the same port.

What we gained

  • The difference between a library and a framework.
  • A working web server in six lines: app = Flask(__name__), a route for / and a function that returns text.
  • How FLASK_APP tells Flask which file to run.
  • A habit of testing the route with Flask's test client instead of a browser.

In this repository

Code: src/flask_day_54/presentation/hello.py (route hello_world), the use case application/get_greeting.py and the constant GREETING. Tests: tests/e2e/test_hello_app.py.

Flask Day 54

Languages

Flask Day 54 - Udemy 100 Days of Code. Code, tests and project documents: repository.