README.md

Error Handling and Defensive Programming (Python)

This module teaches robust validation checks and safe failure behavior.

Learning Metadata

• Difficulty: Intermediate.
• Estimated Time: 30-45 minutes.
• Prerequisites: 02-core/input-validation, 02-core/file-io-basics.
• Cross-Language Lens: Compare exceptions, error returns, and guard-style validation as different ways to keep programs safe.

Quick Run

python example/main.py

Topics Covered

• Defensive input validation with retry logic.
• Early returns for invalid states.
• Guard conditions before risky operations.
• Producing clear and actionable error messages.

Common Pitfalls

• Continuing execution after detecting invalid input.
• Performing division without zero checks.
• Catching errors without giving useful user feedback.

Exercise Focus

• exercises/01.py: validate CSV-like row format.
• exercises/02.py: safe division utility with retries.

Exercise Specs

1. exercises/01.py

• Input: one row with format name,age,city.
• Output: parsed fields or invalid format message.
• Edge cases: missing commas; empty fields.

2. exercises/02.py

• Input: pairs of numbers for division until valid.
• Output: quotient or error/retry message.
• Edge cases: divisor zero; non-numeric input.

Checkpoint

• I can guard risky operations with clear checks.
• I can stop invalid program paths early.
• I can produce useful error feedback for users.
• I completed exercises/01.py.
• I completed exercises/02.py.