CodeToLive

Introduction to Flask

Flask is a lightweight WSGI web application framework in Python. It's designed to make getting started quick and easy, with the ability to scale up to complex applications.

What is Flask?

Flask is:

• A micro web framework written in Python
• Based on Werkzeug WSGI toolkit and Jinja2 template engine
• Extremely lightweight and modular
• Great for small to medium web applications and APIs

Installation

# Create and activate a virtual environment
python -m venv venv
source venv/bin/activate  # Linux/Mac
venv\Scripts\activate    # Windows

# Install Flask
pip install flask
            

Minimal Flask Application

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

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

Key Features

• Routing: Easy URL routing with decorators
• Templates: Jinja2 templating engine
• Development Server: Built-in development server
• Request Handling: Request and response objects
• Extensions: Modular design with extensions

Project Structure

flask_app/
├── app.py          # Main application file
├── static/         # Static files (CSS, JS, images)
│   ├── style.css
│   └── script.js
└── templates/      # HTML templates
    └── index.html
            

Running the Application

# Run the development server
flask run

# Or alternatively
python app.py
            

Debug Mode

Enable debug mode for automatic reloading and better error messages:

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

Configuration

app.config['SECRET_KEY'] = 'your-secret-key'
app.config['DEBUG'] = True
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///site.db'
            

Next Steps

Now that you have a basic Flask application running, you can explore:

• Creating more complex routes
• Working with templates
• Handling form submissions
• Connecting to databases