🧱

Python Basics — Variables, Types & Control Flow

The essential syntax you'll use in every automation script you write.

⏱14 min read📚DevOps Fundamentals

Every automation script is built from the same handful of ideas: storing values, choosing between data types, grouping data in collections, making decisions, and repeating work. This lesson covers all of them.

🎯 Learning Objectives

By the end of this lesson you will:

Use variables and Python’s core data types
Work with lists and dictionaries
Write conditionals (if / elif / else)
Loop with for and while

Variables and Data Types

Python figures out the type for you — no declarations needed:

python

name = "web-server-01"     # string
cpu_count = 4              # integer
load_average = 0.75        # float
is_healthy = True          # boolean

print(name, cpu_count, load_average, is_healthy)

bash — 80×24

student@devops:~$python3 basics.py

web-server-01 4 0.75 True

Collections: Lists and Dictionaries

These two structures carry most DevOps data (servers, configs, API responses).

A list — an ordered sequence:

python

servers = ["web-01", "web-02", "db-01"]

print(servers[0])        # web-01
print(len(servers))      # 3
servers.append("web-03") # add one

A dictionary — key/value pairs (just like JSON):

python

server = {
  "name": "web-01",
  "cpu": 4,
  "region": "eu-west-1",
}

print(server["region"])   # eu-west-1

💡 Dictionaries = JSON

API responses and config files are almost always key/value data. Python dictionaries map onto JSON directly, which is why they show up constantly in DevOps scripts.

Making Decisions: if / elif / else

python

load = 0.85

if load > 0.9:
  print("CRITICAL: scale up now")
elif load > 0.7:
  print("WARNING: load is high")
else:
  print("OK")

⚠ Indentation is the syntax

Python has no braces — indentation defines blocks. Use 4 spaces consistently. Mixing tabs and spaces is the classic beginner error and will raise an IndentationError.

Loops

Loop over a list with for:

python

servers = ["web-01", "web-02", "db-01"]

for server in servers:
  print(f"Checking {server}...")

bash — 80×24

student@devops:~$python3 loop.py

Checking web-01...
Checking web-02...
Checking db-01...

Repeat while a condition holds with while:

python

attempts = 0
while attempts < 3:
  print(f"Retry {attempts + 1}")
  attempts += 1

💡 f-strings

f"Checking {server}" is an f-string — it drops variables straight into text. It’s the cleanest way to build log lines and messages, and you’ll use it everywhere.

🧪 Hands-on Lab

📝

Server Health Reporter

Create a list of 3 server names.
Loop over them and print "<name> is being checked" using an f-string.
Make a dictionary describing one server (name, cpu, region) and print its region.
Add an if/else that prints "scale up" when a load variable is above 0.8.

✅

Official Solution

python

servers = ["web-01", "web-02", "db-01"]
for s in servers:
  print(f"{s} is being checked")

box = {"name": "web-01", "cpu": 4, "region": "eu-west-1"}
print(box["region"])

load = 0.92
print("scale up" if load > 0.8 else "ok")

🧠 Knowledge Check

Knowledge Check

Which Python data structure best represents a JSON object with key/value pairs?

A listA dictionaryA stringA boolean

Knowledge Check

What defines a block of code in Python (e.g. the body of an if statement)?

Curly braces { }The 'end' keywordIndentation (whitespace)Semicolons

💼 Interview Preparation

Interview Q&A

What's the difference between a list and a dictionary, and when would you use each?

Summary

You’ve covered variables, data types, lists, dictionaries, conditionals, and loops — the foundation of every script. Next, we put it to work automating real DevOps tasks.

Up Next

Automating Tasks with Python

You've mastered this lesson. Continue your journey to becoming a DevOps Engineer.

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