Week 1 - Day 3: Conditions & Loops

Duration: 5 Hours

📚 Learning Objectives

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

Write conditional statements with if, elif, else
Use comparison and logical operators
Create for loops to iterate over sequences
Use while loops for conditional iteration
Control loop flow with break and continue

📖 Core Concepts (2 Hours)

Conditional Statements: if

Conditionals let your program make decisions based on conditions.

                    
# Basic if statement
age = 20

if age >= 18:
    print("You are an adult")

# With else
temperature = 35

if temperature > 30:
    print("It's hot!")
else:
    print("It's comfortable")

# DevOps example
cpu_usage = 85

if cpu_usage > 80:
    print("⚠️ Warning: High CPU usage!")
else:
    print("✓ CPU usage normal")
                    
                

Multiple Conditions: elif

                    
# elif = else if
score = 75

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
elif score >= 60:
    grade = "D"
else:
    grade = "F"

print(f"Your grade: {grade}")

# DevOps: Server status check
status_code = 503

if status_code == 200:
    print("✓ OK - Service running")
elif status_code == 404:
    print("✗ Not Found")
elif status_code == 500:
    print("✗ Internal Server Error")
elif status_code == 503:
    print("✗ Service Unavailable")
else:
    print(f"Unknown status: {status_code}")
                    
                

Comparison Operators

                    
# Comparison operators return True or False
x = 10
y = 5

print(x == y)    # False (equal to)
print(x != y)    # True  (not equal to)
print(x > y)     # True  (greater than)
print(x < y)     # False (less than)
print(x >= y)    # True  (greater or equal)
print(x <= y)    # False (less or equal)

# String comparison
name = "admin"
if name == "admin":
    print("Welcome, administrator!")

# Checking membership
if "log" in "/var/log/syslog":
    print("This is a log file path")
                    
                

Logical Operators

                    
# and, or, not

# and - both must be True
age = 25
has_license = True

if age >= 18 and has_license:
    print("You can drive")

# or - at least one must be True
day = "Saturday"

if day == "Saturday" or day == "Sunday":
    print("It's the weekend!")

# not - reverses the boolean
is_maintenance = False

if not is_maintenance:
    print("System is operational")

# Complex conditions
cpu = 70
memory = 85
disk = 90

if cpu > 80 or memory > 80 or disk > 80:
    print("⚠️ Resource alert!")

if cpu < 80 and memory < 80 and disk < 80:
    print("✓ All resources OK")
                    
                

Nested Conditions

                    
# Conditions inside conditions
user = "admin"
password = "secret123"
is_active = True

if user == "admin":
    if password == "secret123":
        if is_active:
            print("Access granted!")
        else:
            print("Account disabled")
    else:
        print("Wrong password")
else:
    print("User not found")

# Cleaner with and
if user == "admin" and password == "secret123" and is_active:
    print("Access granted!")
                    
                

For Loops

                    
# Iterate over a sequence

# Loop through a list
servers = ["web-01", "web-02", "db-01"]
for server in servers:
    print(f"Checking {server}...")

# Loop through a string
for char in "Python":
    print(char)

# Loop with range()
for i in range(5):          # 0, 1, 2, 3, 4
    print(f"Iteration {i}")

for i in range(1, 6):       # 1, 2, 3, 4, 5
    print(f"Server-{i}")

for i in range(0, 10, 2):   # 0, 2, 4, 6, 8
    print(i)

# Loop with index using enumerate()
fruits = ["apple", "banana", "cherry"]
for index, fruit in fruits:
    print(f"{index}: {fruit}")
                    
                

While Loops

                    
# Loop while condition is True

# Basic while loop
count = 0
while count < 5:
    print(f"Count: {count}")
    count += 1

# DevOps: Retry logic
attempts = 0
max_attempts = 3
connected = False

while attempts < max_attempts and not connected:
    attempts += 1
    print(f"Connection attempt {attempts}...")
    # Simulate connection (would be real code)
    if attempts == 3:
        connected = True

if connected:
    print("✓ Connected!")
else:
    print("✗ Failed to connect")

# User input loop
while True:
    response = input("Continue? (yes/no): ")
    if response.lower() == "no":
        print("Goodbye!")
        break
                    
                

Break and Continue

                    
# break - exit the loop immediately
for i in range(10):
    if i == 5:
        print("Found 5, stopping!")
        break
    print(i)
# Output: 0, 1, 2, 3, 4, Found 5, stopping!

# continue - skip to next iteration
for i in range(10):
    if i % 2 == 0:  # Skip even numbers
        continue
    print(i)
# Output: 1, 3, 5, 7, 9

# DevOps: Process only active servers
servers = [
    {"name": "web-01", "active": True},
    {"name": "web-02", "active": False},
    {"name": "db-01", "active": True},
]

for server in servers:
    if not server["active"]:
        continue
    print(f"Processing {server['name']}")
                    
                

Loop with else

                    
# else runs if loop completes without break

# Search example
numbers = [1, 3, 5, 7, 9]
target = 4

for num in numbers:
    if num == target:
        print(f"Found {target}!")
        break
else:
    print(f"{target} not found in list")

# DevOps: Check all services
services = ["nginx", "mysql", "redis"]
for service in services:
    status = "running"  # Would check actual status
    if status != "running":
        print(f"✗ {service} is down!")
        break
else:
    print("✓ All services running!")
                    
                

🔬 Hands-on Lab (2.5 Hours)

Lab 1: Grade Calculator

Get a score from user input
Use if/elif/else for grade
Add pass/fail status

                    
# Lab 1: grade_calculator.py

print("=== Grade Calculator ===")
score = int(input("Enter your score (0-100): "))

# Determine grade
if score >= 90:
    grade = "A"
    status = "Excellent!"
elif score >= 80:
    grade = "B"
    status = "Good job!"
elif score >= 70:
    grade = "C"
    status = "Satisfactory"
elif score >= 60:
    grade = "D"
    status = "Needs improvement"
else:
    grade = "F"
    status = "Failed"

# Pass/Fail
passed = score >= 60

print()
print(f"Score: {score}")
print(f"Grade: {grade}")
print(f"Status: {status}")
print(f"Result: {'PASS' if passed else 'FAIL'}")
                    
                

Lab 2: Number Guessing Game

Generate a random number
Use while loop for guesses
Provide hints (higher/lower)

                    
# Lab 2: guessing_game.py
import random

print("=== Number Guessing Game ===")
print("I'm thinking of a number between 1 and 100")
print()

secret = random.randint(1, 100)
attempts = 0
max_attempts = 7

while attempts < max_attempts:
    guess = int(input("Your guess: "))
    attempts += 1
    
    if guess == secret:
        print(f"🎉 Correct! You got it in {attempts} attempts!")
        break
    elif guess < secret:
        print("📈 Higher!")
    else:
        print("📉 Lower!")
    
    remaining = max_attempts - attempts
    if remaining > 0:
        print(f"   ({remaining} attempts remaining)")
else:
    print(f"😢 Game over! The number was {secret}")
                    
                

Lab 3: Server Health Monitor

Loop through server list
Check CPU, memory, disk
Alert on high usage

                    
# Lab 3: health_monitor.py

print("=" * 50)
print("       SERVER HEALTH MONITOR")
print("=" * 50)

# Simulated server data
servers = [
    {"name": "web-01", "cpu": 45, "memory": 60, "disk": 70},
    {"name": "web-02", "cpu": 85, "memory": 75, "disk": 65},
    {"name": "db-01", "cpu": 30, "memory": 90, "disk": 85},
    {"name": "cache-01", "cpu": 20, "memory": 40, "disk": 30},
]

# Thresholds
CPU_THRESHOLD = 80
MEMORY_THRESHOLD = 80
DISK_THRESHOLD = 80

alerts = []

for server in servers:
    name = server["name"]
    print(f"\nChecking {name}...")
    
    # Check each metric
    if server["cpu"] > CPU_THRESHOLD:
        alert = f"  ⚠️ {name}: High CPU ({server['cpu']}%)"
        print(alert)
        alerts.append(alert)
    
    if server["memory"] > MEMORY_THRESHOLD:
        alert = f"  ⚠️ {name}: High Memory ({server['memory']}%)"
        print(alert)
        alerts.append(alert)
    
    if server["disk"] > DISK_THRESHOLD:
        alert = f"  ⚠️ {name}: High Disk ({server['disk']}%)"
        print(alert)
        alerts.append(alert)
    
    # All OK?
    if (server["cpu"] <= CPU_THRESHOLD and 
        server["memory"] <= MEMORY_THRESHOLD and 
        server["disk"] <= DISK_THRESHOLD):
        print(f"  ✓ {name}: All metrics OK")

# Summary
print("\n" + "=" * 50)
print("SUMMARY")
print("=" * 50)
print(f"Servers checked: {len(servers)}")
print(f"Alerts generated: {len(alerts)}")

if alerts:
    print("\nAll Alerts:")
    for alert in alerts:
        print(alert)
else:
    print("\n✓ No alerts - all systems healthy!")
                    
                

Lab 4: Menu System

Create an interactive menu
Use while loop for persistence
Handle invalid choices

                    
# Lab 4: menu_system.py

def show_menu():
    print("\n=== DevOps Tools Menu ===")
    print("1. Check server status")
    print("2. View logs")
    print("3. Deploy application")
    print("4. Backup database")
    print("5. Exit")
    print()

while True:
    show_menu()
    choice = input("Select option (1-5): ")
    
    if choice == "1":
        print("\n📊 Checking server status...")
        print("   All servers operational!")
    
    elif choice == "2":
        print("\n📋 Recent logs:")
        print("   [INFO] Application started")
        print("   [INFO] Connection established")
        print("   [WARN] High memory usage detected")
    
    elif choice == "3":
        confirm = input("\n⚠️ Deploy to production? (yes/no): ")
        if confirm.lower() == "yes":
            print("🚀 Deploying application...")
            print("✓ Deployment successful!")
        else:
            print("Deployment cancelled.")
    
    elif choice == "4":
        print("\n💾 Starting backup...")
        for i in range(1, 4):
            print(f"   Backing up table {i}/3...")
        print("✓ Backup complete!")
    
    elif choice == "5":
        print("\nGoodbye! 👋")
        break
    
    else:
        print("\n❌ Invalid option! Please choose 1-5.")
                    
                

📝 Practice Exercises

Write a FizzBuzz program (1-100: Fizz for 3, Buzz for 5, FizzBuzz for both)
Create a login system with 3 attempts maximum
Build a multiplication table generator
Write a program that finds prime numbers up to N

💡 DevOps Relevance

Why this matters:

Conditions: Health checks, status validation, routing logic
For loops: Iterate servers, process logs, bulk operations
While loops: Retry logic, polling, waiting for conditions
Break/Continue: Error handling, skip inactive resources

✅ Day 3 Checklist

Can write if/elif/else statements
Understand comparison operators
Can use logical operators (and, or, not)
Can create for loops with range()
Can create while loops
Know when to use break and continue

← Day 2: Variables & Data Types Day 4: Functions →