Django Overview and Setup

Overview

This lecture introduces Django, covering setup, key concepts, project structure, debugging, and data modeling for an e-commerce backend. You'll learn how to start a project, create apps, define models, and best practices for organizing code.

Introduction to Django

• Django is a free, open-source web framework built with Python, popular for rapid web application development.
• It is "batteries included," providing features like admin interface, ORM (Object Relational Mapper), authentication, and caching out of the box.
• Django has a large, active community and is used by major companies (YouTube, Instagram, Spotify).

Prerequisites & Setup

• You need to know Python basics and object-oriented programming (classes, inheritance, polymorphism).
• Basic knowledge of relational databases (tables, columns, primary/foreign keys) is required.
• Use the latest Python version and install Visual Studio Code with the Python extension for development.
• Install Django in a virtual environment using pip or pipenv.

Project Structure & Apps

• A Django project is a collection of apps, each providing specific functionalities.
• Use django-admin startproject to create a new project directory.
• Use python manage.py startapp <app_name> to create new apps, e.g., playground.
• Register each new app in the INSTALLED_APPS list in settings.py.

URLs, Views, and Templates

• Views are request handlers (functions) that return responses, not visual elements; templates handle HTML rendering.
• Map URLs to view functions in an app's urls.py and include them in the main project's urls.py.
• Use Django's template system for dynamic HTML, passing context data from views.

Debugging Tools

• Integrated VS Code debugger allows step-by-step execution and variable inspection.
• Set up a launch.json file for Django debugging in VS Code.
• Use Django Debug Toolbar for advanced debugging info, like SQL queries.

Web Development Fundamentals

• Web apps have front-end (client, visible to users) and back-end (server, processes data).
• HTTP (HyperText Transfer Protocol) handles client-server communication.
• Django is a back-end (server-side) framework, not to be confused with front-end frameworks like React.

API Focus in Django

• Django is commonly used to build APIs for client apps, exchanging data rather than HTML.
• Endpoints represent server functionality and are defined as part of the app's API.

Data Modeling in Django

• Identify core entities for an e-commerce app: Product, Collection (Category), Cart, Customer, Order, Tag.
• Define relationships: one-to-many (e.g. Collection to Product), many-to-many (e.g. Product to Cart via CartItem).
• Use association classes (e.g. CartItem, OrderItem) to model relationships with extra attributes like quantity.

App Organization Best Practices

• Avoid monolithic (all-in-one) apps; don’t split too granularly either.
• Group highly cohesive models (e.g., store features) together; separate reusable parts (e.g., tags) into distinct apps.
• Register all apps in INSTALLED_APPS for Django to recognize them.

Key Terms & Definitions

• Django — Python web framework for building server-side applications.
• Virtual Environment — Isolated environment to manage dependencies.
• App — Self-contained module within a Django project for a specific feature.
• View — Function handling HTTP requests and returning responses.
• Template — HTML file for rendering dynamic content.
• Model — Class representing database tables/entities.
• URLconf — URL configuration mapping URLs to views.
• ORM (Object Relational Mapper) — Abstraction layer for database operations.
• API (Application Programming Interface) — Set of endpoints for client-server data exchange.

Action Items / Next Steps

• Upgrade Python to the latest version and install Visual Studio Code and Python extension.
• Install Django in a virtual environment and create your first project.
• Create and register at least one new app.
• Practice mapping URLs to views and rendering templates.
• Complete the exercise: Identify five core entities for an ecommerce app and their relationships.
• Prepare to implement model classes for the defined entities.