Lecture Notes on 12 Factor App and Command Line Programming

Introduction to the 12 Factor App

• A methodology for building software-as-a-service apps.
• Covers areas such as codebase, version control, and dependencies.

Midterm Project Overview

• Develop a command-line application.
• Due after spring break.
• Must address several design patterns and factors.
• Includes a written paper explaining design patterns with code illustrations.

Importance of Design Patterns

• Design patterns are part of the vocabulary and habits for professional developers.
• Key design patterns: SOLID (Single Responsibility, Open/Closed, Liskov Substitution).
• Helps in building robust and maintainable code.
• Design patterns are crucial for industry standards and expectations.

Command Pattern and REPL

• Command Pattern: Used to manage input and output in applications.
• REPL (Read-Evaluate-Print Loop): A fundamental programming model similar to most interactive programs.
  • Takes user input, evaluates it, prints results, and loops.
• Example implementation involves Python command line with simple commands like exit, hello, goodbye.

Abstract Classes and Interfaces

• Abstract Class: A template for classes that implement its functionality.
• Interfaces: A contract between a class and its expected behaviors.
• Abstract classes in Python require implementation of certain methods, enforced through inheritance.

Practical Application and Development Tips

• Branching Patterns:
  • Development branch is for current work in progress.
  • Feature branches for specific new features.
• Plug-In Architecture: Possible to automate command registration using plugins.
• Challenge to implement a plugin system for automatic command registration.

Error Handling and Code Efficiency

• EAFP (Easier to Ask for Forgiveness than Permission): Error handling strategy using try-except blocks.
• Alternative to using if-statements for handling predictable errors.
• More efficient in scenarios where errors are less likely.

Software Development Mindset

• Industry requires conformity to certain standards and practices.
• Design patterns and a structured approach open opportunities for advanced programming tasks.
• Understanding and using these concepts enhance employability and coding proficiency.

Homework and Practice

• Create a new repository for midterm project.
• Implement at least one new command in the project.
• Start learning about design patterns using resources like Refactor Guru.

Conclusion

• Focus on mastering object-oriented design and understanding software development fundamentals.
• Future classes will cover programming with data and using libraries like Pandas and NumPy.
• Importance of combining understanding of design patterns with algorithms for complete proficiency.