README.md

Input Validation (Python)

This module teaches defensive input handling for interactive programs.

Learning Metadata

• Difficulty: Intermediate.
• Estimated Time: 30-45 minutes.
• Prerequisites: 01-foundations/control-flow, 01-foundations/types-and-io.
• Cross-Language Lens: Compare loop-driven validation in all four languages and notice where parsing APIs are strict versus forgiving.

Quick Run

python example/main.py

Topics Covered

• Validating integer and floating-point input with retry loops.
• Rejecting values outside accepted ranges.
• Reusing input-validation helpers to avoid duplicated logic.
• Keeping interactive programs stable when users type invalid data.

Common Pitfalls

• Calling int() or float() once and crashing on invalid input.
• Accepting out-of-range values after successful parsing.
• Repeating similar validation logic instead of extracting helpers.

Exercise Focus

• exercises/01.py: read an integer in range 1 to 100 and print its square.
• exercises/02.py: read a valid score count and valid scores, then print average.

Exercise Specs

1. exercises/01.py

• Input: repeated attempts until a valid integer in range 1..100 is entered.
• Output: square of the accepted value.
• Edge cases: non-integer text; values below 1 or above 100.

2. exercises/02.py

• Input: score count in range 1..50, followed by scores in range 0..100.
• Output: average score.
• Edge cases: invalid value in the middle of score entry; boundary values 0 and 100.

Checkpoint

• I can recover from type parsing errors without crashing.
• I can validate numeric ranges with retry loops.
• I can reuse helper functions for multiple validated inputs.
• I completed exercises/01.py.
• I completed exercises/02.py.