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Chapter 22: IO and File Handling

Welcome to Chapter 22, where you'll master input/output operations—the foundation of every useful program. You'll learn how programs interact with users through the console, persist data to files for long-term storage, organize file systems using cross-platform paths, and work with structured data formats like CSV and JSON. By the end, you'll build a complete Note-Taking CLI application that integrates all these concepts.

This chapter applies the AI-Native Learning methodology you've practiced since Chapter 1: you describe what you want your code to do, explore concepts with your AI companion, validate your understanding through interactive programs, and learn from errors by asking "why?" This is the same pattern you'll use throughout your professional career.

What You'll Learn​

By the end of this chapter, you will be able to:

  1. Gather and validate console input with proper error handling and formatted output (Lesson 1)
  2. Read and write files safely using context managers and exception handling (Lesson 2)
  3. Work with file paths across Windows, Mac, and Linux using pathlib (Lesson 3)
  4. Load and save structured data in CSV and JSON formats with correct encoding (Lesson 4)
  5. Build a complete CLI application integrating all I/O concepts (Lesson 5 - Capstone)

A Note on AI Collaboration​

This chapter assumes you have access to Claude Code or Gemini CLI (or a similar AI tool). Every "Try With AI" section references your AI companion. If you don't have access yet, revisit Chapters 5-6 to set up your tool before proceeding.

Your AI tool isn't a crutch—it's a partner in learning. Use it to:

  • Clarify concepts
  • Validate your code
  • Understand error messages
  • Review your work
  • Explore extensions
  • Reflect on your learning

Professional developers use AI daily. Learning to use it effectively is a core skill this chapter teaches.