Overview

What is Python?¶

Python is the go-to language for IT automation because of:

Readable syntax — easy to learn and maintain
Extensive libraries — Netmiko, NAPALM, Paramiko, Requests, etc.
Cross-platform — runs on Windows, Linux, macOS
Dynamic typing — no need to declare variable types
Large community — tons of resources and pre-built solutions

Subcategories¶

Quick Reference — Key Rules to Remember¶

Concept	The Rule
Variables	Created on assignment — no declaration needed
`=` vs `==`	`=` assigns a value; `==` compares two values — mixing these up is a common bug
`is` vs `==`	`is` checks if two variables are the same object in memory; `==` checks if values are equal
Indentation	4 spaces = one code block level. Missing or wrong indentation is a SyntaxError
List `[]`	Ordered, mutable — you can add, change, and remove items
Tuple `()`	Ordered, immutable — contents are fixed after creation
Dict `{}` with `:`	Key-value pairs — look up values by key, not by position
Set `{}` no `:`	Unordered, unique items only — great for deduplication
`for x in y`	Loops over every item in y, one at a time
`while condition`	Loops as long as condition is `True` — always update something to avoid infinite loops
`break`	Exit the loop immediately
`continue`	Skip to the next loop iteration
`def`	Defines a reusable function
`return`	Sends a value back from a function — without it, function returns `None`
`try / except`	Wraps risky code — if an error occurs, `except` runs instead of crashing
`with open()`	Best way to work with files — automatically closes the file when done
`"r"` / `"w"` / `"a"`	Read / Write (overwrites everything) / Append (adds to end)
`.strip()`	Removes leading/trailing whitespace and `\n` newline characters from a string
`.readlines()`	Reads all lines from a file into a list of strings
`csv.reader()`	Creates a reader object to loop through rows of a CSV file
`next(reader)`	Reads one row from a CSV reader — use this for the header row
`os.path.exists()`	Check if a file/folder exists before trying to open, delete, or modify it
`os.remove()`	Delete a file
`filecmp.cmp()`	Compare two files — returns `True` if identical
`import`	Load a module or library so you can use its functions
`help()`	View built-in documentation for any function, method, or module
`pip install`	Install a third-party library from the command line