Flask is a micro web framework written in Python . It is called a microframework because in the framework itself is no-frills added and comes without any feature bundled in.

More advanced web frameworks such as Django has almost everything needed to build a fully functioning website such as DB handling, user, and session management, etc.
Flask on the other hand, has almost nothing but supports extensions that can be used to bring in these features. Microframeworks are preferred by many because it is lightweight but still extensible to add any feature with ready to use plugins.

Key Features of Flask

1. Lightweight and Modular:

   • Flask is designed to be small and extendable, allowing developers to use only the tools and libraries they need. This minimalistic approach helps in keeping the codebase clean and understandable.

2. Routing:

   • Flask uses a simple routing system that maps URLs to Python functions. This allows developers to define what should happen when a user accesses a particular URL. For example, you can define a route for the home page (/) and another for an about page (/about).

3. Template Engine:

   • Flask uses Jinja2, a powerful template engine, to render HTML pages. Jinja2 allows developers to use variables, loops, and conditionals in their HTML templates, making it easy to create dynamic content.

4. Extensions:

   • While Flask itself is minimal, it has a rich ecosystem of extensions that can be added to provide additional functionality. These extensions cover areas such as database integration, form handling, authentication, and more.

5. Easy to Learn:

   • Flask has a straightforward and readable syntax, making it a great choice for beginners who want to learn web development with Python. The simplicity of Flask also allows developers to focus on learning the core concepts of web development without getting overwhelmed by complex frameworks.

Example of Simple Falsk Application

Here is the  basic exapmle of flask application

pip install Flask

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return "Hello, Flask!"

@app.route('/about')
def about():
    return "This is the about page."

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

Explanation of the Code:

1. Importing Flask:

   • The Flask class is imported from the flask module.

2. Creating an Application Instance:

   • app = Flask(__name__) creates an instance of the Flask class. The __name__ argument helps Flask determine the root path of the application, which is useful for resource loading.

3. Defining Routes:

   • The @app.route('/') decorator defines a route for the home page. When a user accesses the root URL (/), the home function is called, returning "Hello, Flask!".
   • Similarly, the @app.route('/about') decorator defines a route for the about page.

4. Running the Application:

   • app.run(debug=True) starts the development server and allows the application to be accessible via a web browser. The debug=True option enables debug mode, which provides detailed error messages and auto-restarts the server when code changes are detected.

Run your Fals app

python app.py

You should see output indicating that the Flask server is running. Open a web browser and go to http://127.0.0.1:5000/ to see your first Flask app in action!

you can simply run flask appliaction as

Then open terminal and write below command to run flask application as

Some important terms in flask

1. templates : Flask application looks for HTML pages that will be displayed in
the browser in this folder by default
2. static : Is used to keep any static files that are used in the templates. This
includes images, logos, JavaScript files, and CSS Stylesheets

Basic Flask Syntax:

Models in Flask

if you want to connect mysql database then follow below process

At the first time you need to initialize database by running below commnad

Generate Migration: Use Flask-Migrate to generate a migration script based on the changes in your models.

Run the following command in your terminal:

Apply Migration: Once the migration script is generated, you need to apply it to your database to make the actual changes.

Run the following command:

Static file

Authentication
 

__init__.py

other info