README.md

File I/O Basics (Python)

This module teaches safe text-file reading and writing with beginner-friendly patterns.

Learning Metadata

• Difficulty: Intermediate.
• Estimated Time: 30-45 minutes.
• Prerequisites: 01-foundations/types-and-io, 01-foundations/strings.
• Cross-Language Lens: Compare text-file APIs, line parsing, and error handling styles while keeping the workflow conceptually identical.

Quick Run

python example/main.py

Topics Covered

• Reading files line by line with context managers.
• Writing summary files safely with explicit output paths.
• Parsing name score rows with split and integer conversion.
• Skipping malformed rows while keeping the program stable.

Common Pitfalls

• Assuming input files always exist.
• Parsing rows without checking token count first.
• Letting one malformed row terminate the full run.

Cross-Language Notes

• Python makes file processing compact, so the comparison with C++ and Go highlights how little ceremony is required to read and transform text.
• Compared with C#, the code often becomes shorter, but validation discipline matters just as much.
• The key lesson is that concise I/O does not remove the need for defensive parsing.

Exercise Focus

• exercises/01.py: copy lines from one file to another with line numbers.
• exercises/02.py: parse name score rows, count invalid rows, and compute average.

Exercise Specs

1. exercises/01.py

• Input: source file path and destination file path.
• Output: destination file with numbered lines (1: ..., 2: ...).
• Edge cases: missing source file; empty source file.

2. exercises/02.py

• Input: file path with rows in the format name score.
• Output: valid row count, invalid row count, and average score.
• Edge cases: malformed rows; file with no valid rows.

Checkpoint

• I can open files safely and handle missing paths.
• I can parse and validate simple text rows.
• I can skip malformed data without aborting the run.
• I completed exercises/01.py.
• I completed exercises/02.py.