📌 Key Concepts
| Concept | One-Line Definition |
|---|---|
print() | Built-in function to output data to the terminal |
| Variable | A named container in memory that holds a value |
| Dynamic Typing | Python figures out the data type automatically at runtime |
| Identifier | The name you give to a variable, function, or class |
| Keyword | Reserved words Python uses internally — cannot be used as identifiers |
type() | Built-in function that tells you the data type of a value |
id() | Returns the memory address of an object |
🔤 Syntax
# print() — basic output
print("Hello DevOps")
print(variable_name)
print(value, type(value)) # print value AND its type together
# Variable assignment
port = 8080 # int
service_name = "nginx" # str
cpu_threshold = 85.5 # float
# type() — check data type
print(type(port)) # <class 'int'>
# id() — check memory address
print(id(service_name))
# keyword list
import keyword
print(keyword.kwlist)
# input() — take user input
name = input("Enter your name: ")
print("Hello", name)
🔍 Core Concepts Explained
1. print() Function
The most basic output function. In DevOps scripts, you'll use it constantly to log statuses, debug values, and show results.
print("Deployment started")
print("Server IP:", server_ip)
print("Status:", status, "| Code:", code) # multiple values with comma
2. Variables
A variable is just a label pointing to a value in memory. Think of it like naming a config value so you can reuse it.
# BAD — hardcoded everywhere
# connect("192.168.1.10", 22)
# connect("192.168.1.10", 22)
# GOOD — use a variable
server_ip = "192.168.1.10"
ssh_port = 22
connect(server_ip, ssh_port)
3. Dynamic Typing
Python doesn't require you to declare the type. It detects it automatically. The same variable can hold different types at different times.
a = 10 # int
a = "hello" # now str — Python is fine with this
a = 3.14 # now float
⚠️ Common Mistake: Reassigning a variable to a different type accidentally can cause bugs in automation scripts.
4. Data Types (from class)
| Type | Example | DevOps Use Case |
|---|---|---|
int | port = 22 | Port numbers, exit codes |
float | cpu = 85.5 | CPU/memory thresholds |
str | env = "prod" | Environment names, server IPs |
bool | is_healthy = True | Health check flags |
port = 22 # int
threshold = 85.5 # float
environment = "prod" # str
is_active = True # bool
5. Identifiers — Naming Rules
✅ VALID ❌ INVALID
server_ip 5server (starts with number)
_private server-ip (hyphen = minus operator)
cpu2core server ip (space not allowed)
myVar if (reserved keyword)
EC2Instance print = 100 (shadows built-in — avoid!)
Golden Rule for DevOps Scripts: Use snake_case (lowercase with underscores) — server_ip, max_retries, aws_region. This matches Python convention and is easy to read.
6. Keywords — Off-Limits Names
import keyword
print(keyword.kwlist)
# ['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await',
# 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except',
# 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is',
# 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return',
# 'try', 'while', 'with', 'yield']
7. Don't Shadow Built-ins ⚠️
The class demonstrated this critical mistake:
# ❌ NEVER do this
print = 100 # You just killed the print function!
print("Python") # TypeError: 'int' object is not callable
# ✅ Restart kernel or use del to recover
del print
print("Python") # Works again
Common built-ins to never overwrite: print, input, list, dict, str, int, len, open, type, id
☁️ DevOps / Cloud Use Cases
# AWS EC2 config variables
instance_type = "t2.micro"
region = "ap-south-1" # Mumbai
ami_id = "ami-0abcdef1234567890"
max_instances = 5
spot_price = 0.012 # float — price in USD
# Docker/K8s config
container_port = 8080
replica_count = 3
image_tag = "nginx:1.25"
is_rolling_update = True
# CI/CD pipeline variable
build_status = "SUCCESS"
exit_code = 0 # 0 = success in Linux/bash
artifact_size_mb = 145.7
# Log line output (you'll do this in every script)
print(f"Deploying {image_tag} to {region} with {replica_count} replicas")
print(f"Build: {build_status} | Exit Code: {exit_code}")
❌ Common Mistakes (from class + real world)
| Mistake | Example | Fix |
|---|---|---|
| Typo in function name | prin("Python") | Check spelling — Python gives NameError |
| Shadow a built-in | print = 100 | Never use built-in names as variables |
| Use keywords as names | if = 5 | Use keyword.kwlist to check |
| Start var with number | 5server = "aws" | Start with letter or underscore |
| Space in variable name | server ip = "x" | Use server_ip |
| Wrong case | Print("hi") | Python is case-sensitive — print ≠ Print |
🎯 Interview Points
"Is Python statically or dynamically typed?"
→ Dynamically typed. Types are determined at runtime, not declared. Usetype()to check."What's the difference between
=and==in Python?"
→=assigns a value.==compares two values. Critical distinction inifconditions."What is
id()used for?"
→ Returns memory address. Useful to understand if two variables point to the same object in memory."Can a variable name start with a number?"
→ No. It can start with a letter (A-Z, a-z) or underscore_."What happens if you name a variable
listorprint?"
→ You shadow the built-in. The original function becomes inaccessible in that scope — a common bug."What is dynamic typing and why does it matter in DevOps scripts?"
→ Python auto-detects types, so you must be careful when reading user input or config values — they come in asstrby default, even if they look like numbers.
📚 Knowledge Base (Quick Revision)
# ── PRINT ──────────────────────────────────────────
print("text") # basic
print(var, type(var)) # value + type
print("Label:", value) # label + value
# ── VARIABLES & TYPES ──────────────────────────────
x = 10 # int
x = 3.14 # float
x = "hello" # str
x = True # bool
# ── USEFUL BUILT-INS ───────────────────────────────
type(x) # what type is x?
id(x) # memory address of x
input("Enter: ") # get user input (returns str)
# ── KEYWORDS ───────────────────────────────────────
import keyword
keyword.kwlist # list of all reserved words
# ── IDENTIFIER RULES ───────────────────────────────
# ✅ letters, digits (not first), underscore
# ❌ spaces, hyphens, special chars, keywords, starts with digit
# ── BUILT-IN SAFETY ────────────────────────────────
dir(__builtins__) # list ALL built-in names
# Never use these as variable names!
🏋️ Practice Questions
Easy
- Write a Python script that stores your name, age, and city in variables and prints them with their data types.
- Try assigning
if = 10and run it. What error do you get? Now look upkeyword.kwlistand list 5 keywords you didn't know. - What is the output of this code? Explain why:
a = "8080"
print(a, type(a))
Medium
- Create variables for: EC2 instance type, region, number of replicas, and whether auto-scaling is enabled. Print each with its type. Now reassign
replicasfromintto astr— what changes? - Write a script that takes a server name as input and prints:
"Connecting to: <server_name>". What type doesinput()always return? - Explain with code why
print = 100breaks things and how you would fix it without restarting Python.
DevOps-Focused
Config Validator Script: Write a script that stores 5 deployment config values (instance type, port, region, replica count, environment name). Print each value, its type, and its memoryid. Then changeportfrominttostr(e.g., from8080to"8080") and explain the real-world implication in a comment.
Build Status Logger: Write a script that usesinput()to ask for a build status (SUCCESS/FAILED), stores it in a variable, and prints:"Pipeline result: <status> | Type: <type>". Add a comment explaining why you'd never name this variableinputorprint.
Python for DevOps & Cloud*