Source: Dev.to

📌 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

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)) #

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)

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

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)

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.

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

✅ 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. 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’]

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

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}”)

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

“Is Python statically or dynamically typed?” type() to check.

“What’s the difference between = and == in Python?” = assigns a value. == compares two values. Critical distinction in if conditions.

“What is id() used for?”

“Can a variable name start with a number?” _.

“What happens if you name a variable list or print?”

“What is dynamic typing and why does it matter in DevOps scripts?” str by 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!

Write a Python script that stores your name, age, and city in variables and prints them with their data types. Try assigning if = 10 and run it. What error do you get? Now look up keyword.kwlist and list 5 keywords you didn’t know. What is the output of this code? Explain why:

a = “8080” print(a, type(a))

Create variables for: EC2 instance type, region, number of replicas, and whether auto-scaling is enabled. Print each with its type. Now reassign replicas from int to a str — what changes? Write a script that takes a server name as input and prints: “Connecting to: ”. What type does input() always return? Explain with code why print = 100 breaks things and how you would fix it without restarting Python. 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 memory id. Then change port from int to str (e.g., from 8080 to “8080”) and explain the real-world implication in a comment. Build Status Logger: Write a script that uses input() to ask for a build status (SUCCESS/FAILED), stores it in a variable, and prints: “Pipeline result: | Type: ”. Add a comment explaining why you’d never name this variable input or print. Python for DevOps & Cloud*