A complete guide to Python — from your first line of code to advanced topics like async, decorators, and metaclasses.

Python

Python is one of the most popular programming languages in the world — and for good reason. It is simple enough for beginners to learn quickly, yet powerful enough to build real-world software used by companies like Google, Netflix, Instagram, and NASA.

This section covers Python from the ground up. Whether you have never written a line of code before, or you already know another language and want to learn Python, this guide is built for you.

What you will learn

Basics

Variables, data types, operators, input/output, and type conversion. Start here.

Control Flow

Making decisions with if, elif, else, and pattern matching with match/case.

Loops

for loops, while loops, and controlling them with break, continue, and else.

Functions

Defining functions, arguments, scope, lambda, decorators, and generators.

Data Structures

Lists, tuples, dictionaries, sets, strings, and comprehensions.

Object-Oriented Programming

Classes, inheritance, dunder methods, properties, and dataclasses.

Modules

Importing, the standard library, pip, and virtual environments.

File Handling

Reading and writing files, context managers, and pathlib.

Error Handling

Exceptions, custom errors, and debugging with logging and pdb.

Testing

Writing and running tests with unittest and pytest.

Advanced

Iterators, functional programming, type hints, and metaclasses.

Async

async/await, the event loop, and the asyncio module.

A quick taste of Python

Before diving in, here is what Python looks like. Do not worry about understanding everything yet — just notice how readable it is.

# A simple function that greets someone
def greet(name):
    return f"Hello, {name}!"

print(greet("world"))  # Hello, world!

# A list of numbers and a loop
numbers = [1, 2, 3, 4, 5]

for number in numbers:
    if number % 2 == 0:
        print(f"{number} is even")
    else:
        print(f"{number} is odd")

Python reads almost like plain English. That is intentional — it is one of the core design goals of the language.

How Python compares to JavaScript

If you have already gone through the JavaScript section, here are the biggest differences to keep in mind:

JavaScript	Python
`let x = 5`	`x = 5`
`console.log()`	`print()`
Curly braces `{}` for blocks	Indentation (spaces) for blocks
Semicolons (optional)	No semicolons
`===` for equality	`==` for equality
`null`	`None`
`true` / `false`	`True` / `False`
`// comment`	`# comment`

Python uses indentation (spaces or tabs) to define code blocks instead of curly braces. This is not just style — it is required syntax. Inconsistent indentation causes errors.

Python versions

This guide uses Python 3.10+. Some topics (like match/case pattern matching) require Python 3.10 or newer. Python 2 is no longer supported and should not be used for new projects.

To check your version:

python3 --version
# Python 3.12.0

Ready? Start with the Basics section.

Introduction