Duration: 5 Hours
📚 Learning Objectives
By the end of this session, you will be able to:
- Create and use variables in Python
- Understand the four basic data types: int, float, str, bool
- Convert between data types (type casting)
- Get user input with the input() function
- Perform string operations and formatting
📖 Core Concepts (2 Hours)
What are Variables?
Variables are containers for storing data. Think of them as labeled boxes where you keep information.
# Creating variables (no declaration needed!)
name = "DevOps Engineer"
age = 25
salary = 75000.50
is_employed = True
# Using variables
print(name) # DevOps Engineer
print(age) # 25
# Changing values
age = 26 # Now age is 26
print(age) # 26
# Variable naming rules
user_name = "alice" # snake_case (Python standard)
serverCount = 10 # camelCase (works but not preferred)
MAX_RETRIES = 3 # CAPS for constants
# Invalid names:
# 2name = "error" # Can't start with number
# my-var = "error" # No hyphens
# class = "error" # Can't use reserved words
Data Type: Integers (int)
# Integers are whole numbers (no decimals)
server_count = 10
port = 8080
error_code = -1
large_num = 1_000_000 # Underscores for readability
# Integer operations
a = 15
b = 4
print(a + b) # 19 (addition)
print(a - b) # 11 (subtraction)
print(a * b) # 60 (multiplication)
print(a / b) # 3.75 (division - returns float!)
print(a // b) # 3 (integer division)
print(a % b) # 3 (modulo/remainder)
print(a ** b) # 50625 (power: 15^4)
# Check type
print(type(server_count)) #
Data Type: Floats (float)
# Floats are decimal numbers
cpu_usage = 75.5
temperature = -10.8
pi = 3.14159
# Float operations
price = 19.99
quantity = 3
total = price * quantity
print(total) # 59.97
# Scientific notation
distance = 1.5e10 # 1.5 × 10^10
tiny = 2.5e-5 # 0.000025
# Rounding
value = 3.14159
print(round(value)) # 3
print(round(value, 2)) # 3.14
# Check type
print(type(cpu_usage)) #
Data Type: Strings (str)
# Strings are text - use quotes
name = "Alice"
message = 'Hello, World!'
path = "/var/log/syslog"
# Multi-line strings
description = """This is a
multi-line
string"""
# String operations
first = "Hello"
last = "World"
# Concatenation
full = first + " " + last
print(full) # Hello World
# Repetition
line = "-" * 20
print(line) # --------------------
# Length
print(len("Python")) # 6
# Indexing (starts at 0!)
text = "Python"
print(text[0]) # P
print(text[-1]) # n (last character)
# Slicing
print(text[0:3]) # Pyt
print(text[2:]) # thon
print(text[:4]) # Pyth
# String methods
msg = " hello world "
print(msg.upper()) # " HELLO WORLD "
print(msg.lower()) # " hello world "
print(msg.strip()) # "hello world"
print(msg.replace("world", "python")) # " hello python "
print(msg.split()) # ['hello', 'world']
# Check type
print(type(name)) #
Data Type: Booleans (bool)
# Booleans are True or False
is_running = True
has_error = False
# Comparison operators return booleans
x = 10
y = 5
print(x > y) # True
print(x < y) # False
print(x == y) # False
print(x != y) # True
print(x >= 10) # True
print(x <= 5) # False
# Boolean operations
a = True
b = False
print(a and b) # False (both must be True)
print(a or b) # True (at least one True)
print(not a) # False (opposite)
# Truthy and Falsy values
print(bool(1)) # True
print(bool(0)) # False
print(bool("text")) # True
print(bool("")) # False
print(bool([1,2])) # True
print(bool([])) # False
# Check type
print(type(is_running)) #
Type Conversion
# Converting between types
# String to Integer
age_str = "25"
age_int = int(age_str)
print(age_int + 5) # 30
# String to Float
price_str = "19.99"
price_float = float(price_str)
print(price_float * 2) # 39.98
# Number to String
count = 42
count_str = str(count)
print("Count: " + count_str) # Count: 42
# Float to Integer (truncates!)
value = 3.9
print(int(value)) # 3 (not rounded!)
# Integer to Float
num = 10
print(float(num)) # 10.0
# Check the type
data = "100"
print(type(data)) #
print(type(int(data))) #
User Input with input()
# input() always returns a string!
# Basic input
name = input("Enter your name: ")
print("Hello, " + name + "!")
# Input with type conversion
age = int(input("Enter your age: "))
print("Next year you'll be", age + 1)
# Multiple inputs
first = input("First name: ")
last = input("Last name: ")
full_name = first + " " + last
print("Welcome,", full_name)
# DevOps example
server = input("Enter server name: ")
port = int(input("Enter port number: "))
print(f"Connecting to {server}:{port}")
String Formatting (f-strings)
# f-strings (Python 3.6+) - the modern way!
name = "Alice"
age = 25
salary = 75000.50
# Basic f-string
print(f"Name: {name}")
print(f"Age: {age}")
# Expressions inside
print(f"Next year: {age + 1}")
print(f"Double salary: ${salary * 2}")
# Formatting numbers
pi = 3.14159
print(f"Pi: {pi:.2f}") # Pi: 3.14
price = 1234567.89
print(f"Price: ${price:,.2f}") # Price: $1,234,567.89
# Padding
for i in range(1, 4):
print(f"Server{i:02d}") # Server01, Server02, Server03
# DevOps example
status = "running"
uptime = 99.95
print(f"Service Status: {status.upper()}")
print(f"Uptime: {uptime:.1f}%")
🔬 Hands-on Lab (2.5 Hours)
Lab 1: Variable Practice
- Create variables for: name, age, height, is_student
- Print all variables with their types
- Perform operations on numeric variables
# Lab 1: variables.py
# Create your profile
name = "Your Name"
age = 25
height = 5.9
is_student = False
# Print with types
print(f"Name: {name} ({type(name).__name__})")
print(f"Age: {age} ({type(age).__name__})")
print(f"Height: {height} ({type(height).__name__})")
print(f"Student: {is_student} ({type(is_student).__name__})")
# Calculations
birth_year = 2024 - age
print(f"Birth year: {birth_year}")
Lab 2: Type Conversion
- Convert strings to numbers
- Convert numbers to strings
- Handle conversion errors
# Lab 2: conversion.py
# String to number
port_str = "8080"
port = int(port_str)
print(f"Port + 1: {port + 1}")
cpu_str = "75.5"
cpu = float(cpu_str)
print(f"CPU Usage: {cpu}%")
# Number to string
error_code = 404
message = "Error " + str(error_code) + " - Not Found"
print(message)
# Building connection string
host = "localhost"
port = 5432
db = "myapp"
connection = f"{host}:{port}/{db}"
print(f"Database: {connection}")
Lab 3: User Input Calculator
- Get two numbers from user
- Perform all math operations
- Display formatted results
# Lab 3: calculator.py
print("=== Simple Calculator ===")
print()
# Get input
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))
# Calculations
print()
print("Results:")
print(f" {num1} + {num2} = {num1 + num2}")
print(f" {num1} - {num2} = {num1 - num2}")
print(f" {num1} × {num2} = {num1 * num2}")
print(f" {num1} ÷ {num2} = {num1 / num2:.2f}")
print(f" {num1} ^ {num2} = {num1 ** num2}")
Lab 4: Server Info Script
- Create a DevOps-style info script
- Use all four data types
- Format output professionally
# Lab 4: server_info.py
print("=" * 40)
print(" SERVER STATUS REPORT")
print("=" * 40)
# Server details (all data types!)
hostname = "web-server-01" # str
cpu_cores = 4 # int
memory_gb = 16.0 # float
is_healthy = True # bool
# User input
uptime_hours = int(input("Enter uptime (hours): "))
disk_usage = float(input("Enter disk usage (%): "))
# Display report
print()
print(f"Hostname: {hostname}")
print(f"CPU Cores: {cpu_cores}")
print(f"Memory: {memory_gb} GB")
print(f"Uptime: {uptime_hours} hours ({uptime_hours // 24} days)")
print(f"Disk Usage: {disk_usage:.1f}%")
print(f"Health: {'✓ Healthy' if is_healthy else '✗ Unhealthy'}")
print("=" * 40)
📝 Practice Exercises
- Create a "Mad Libs" program that asks for nouns, verbs, adjectives
- Build a temperature converter (Celsius to Fahrenheit)
- Write a program that calculates BMI from user input
- Create a formatted receipt with item names and prices
💡 DevOps Relevance
Why this matters:
- Variables: Store config values, API keys, server info
- Strings: File paths, URLs, log messages
- Numbers: Ports, thresholds, metrics
- Booleans: Feature flags, health checks
- input(): Interactive deployment scripts
✅ Day 2 Checklist
- Can create and use variables
- Understand int, float, str, bool types
- Can convert between types
- Know how to get user input
- Can format strings with f-strings
- Understand string methods