1. flask-introduction

Introduction to Flask

Flask is a micro web framework written in Python which is based on the Werkzeug toolkit and Jinja2 template engine. Flask is designed to make getting started quick and easy, with the ability to scale up to complex applications.


Here is a basic syntax for creating a Flask application:

from flask import Flask

app = Flask(__name__)

def index():
    return "Hello, World!"

if __name__ == "__main__":


This example creates a web application that listens for requests on the root URL path (/) and returns a response of Hello, World!.


When you run this application and navigate to http://localhost:5000/ in your web browser, you should see the text "Hello, World!" displayed on the page.


The Flask class is used to create an instance of the web application. The @app.route decorator is used to define the URL path that this function should handle. The index() function is just a simple Python function that returns a string.

Finally, the app.run() method is used to start the development web server provided by Flask.


Flask is commonly used for creating web applications of various complexities. It is suitable for creating simple web APIs to full-fledged web applications.

Important Points

  • Flask is designed to be lightweight and easy to use.
  • Flask is extensible with a large number of third party extensions available.
  • Flask is suitable for various web development purposes.


Flask is a powerful and popular web application development framework that makes it easy to create web applications in Python. With its lightweight and flexible design, it's an excellent choice for both beginners and experienced developers alike.

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