Functions & Data Structures

Stage 02 - Functions, Data Structures, and Menus

Building Reusable Code and Working with Data (Python Cybersecurity Learning Path)

Stage 02 Overview

Stage 01 taught you how to write basic Python that runs.

Stage 02 is about writing Python that is reusable, reliable, and structured like real tools.

In this stage you will:

• Write functions that return values (not just print)
• Understand core data types
• Convert between data types safely (casting)
• Use try/except for robust input validation (no crashes)
• Learn the basics of lists and dictionaries
• Build two practical tools:

- Temperature Converter

- Password Strength Checker (security challenge)

What You Will Build

Tool 1: Temperature Converter

A menu-driven converter that:

• Converts Fahrenheit → Celsius
• Converts Celsius → Fahrenheit
• Uses safe numeric input handling with try/except
• Displays clean output formatting (e.g., :.2f)

Tool 2: Password Strength Checker (Security Challenge)

A password checker that:

• Scores password strength from 0 to 6
• Evaluates:

- length (8+ and 12+)

- uppercase letters

- lowercase letters

- numbers

- special characters

• Returns multiple values from a function (score + feedback)
• Uses a dictionary to map score → rating (cleaner than long if/elif)

Folder Structure

stage_02_Functions_Data_Structures/
└── app/
└── main.py

How to Run

You can run this stage in two supported ways.

Option A (Recommended): Run from the Repository Root

PowerShell (Windows):

python stage_02_Functions_Data_Structures\app\main.py

macOS / Linux:

python app/main.py

Success Checklist (Stage 02 Complete When…)

Functions and Return Values

• You can explain the difference between print() and return

• You can call a function and store its returned value in a variable

Data Types and Conversion

• You can identify and explain:

- str, int, float, bool

• You can safely convert user input to numeric types

Robust Input Validation

• Your program does not crash when the user enters invalid input

• Invalid input is handled using try/except and re-prompts the user

Lists and Dictionaries

• You can explain what lists and dictionaries are used for

• Your program uses a dictionary for password score → rating mapping

Temperature Converter

• Fahrenheit → Celsius works correctly

• Celsius → Fahrenheit works correctly

Results display with appropriate decimal formatting

Password Strength Checker

• Correctly checks length requirements

• Correctly detects uppercase, lowercase, digits, and special characters

• Provides clear improvement suggestions when needed

Code Quality

• Proper indentation (4 spaces)

• Functions are used instead of repeated code

Git and GitHub

• All changes committed to Git

• Changes pushed to GitHub

• Git Commands for Completion

From your repository root folder:

git status
git add stage_02_Functions_Data_Structures
git commit -m "Complete Stage 02 - Functions, Data Structures, and Menus"
git push

Do not proceed to Stage 03 without a clean commit and push.

What’s Next (Stage 03 Preview)

In Stage 03, you will learn to work with files and build more advanced automation tools:

• File I/O: read/write files
• Log analysis (security-relevant)
• CLI arguments (flags like --help)
• JSON data handling
• Automation tools that process data automatically