nonobie — Real dev skills, explained like a friend would

What you'll learn

By the end of this chapter you will:

Install Python 3.12+ from python.org and verify it from the terminal
Use the py launcher on Windows and python3 on macOS/Linux without confusion
Configure VS Code with the official Python extension and a readable theme
Recover from the three most common installation failures

The why

A broken setup kills more beginners than syntax ever will. If you can't run a Python file, you can't learn Python. The good news: installing Python takes 5 minutes. The bad news: there are three common mistakes that waste hours.

This chapter walks you through the setup on Windows, macOS, and Linux. Follow the section for your OS, then verify the installation. If something breaks, check the "Common mistakes" section at the end.

Core concepts: What you're installing

Before we start, understand what you're installing and why:

Python InterpreterOpen section

Let's learn

When you install Python from python.org, you're installing CPython — the standard implementation of the Python language. It's written in C (hence the name) and is the most widely used Python interpreter.

The interpreter does three things:

Parses your Python source code into an AST (Abstract Syntax Tree)
Compiles the AST into bytecode (platform-independent instructions)
Executes the bytecode on the Python Virtual Machine (PVM)

Other interpreters exist (PyPy for speed, MicroPython for embedded devices, Jython for Java integration), but CPython is what you want for learning.

pip — Package InstallerOpen section

Let's learn

pip is Python's package installer. It downloads and installs libraries from PyPI (Python Package ), a repository of 500,000+ packages.

bash

pip install requests        # Install a package
pip install requests==2.28  # Install specific version
pip list                    # List installed packages
pip freeze > requirements.txt  # Save dependencies

pip is included with Python 3.4+. If you have Python 3, you have pip.

Virtual EnvironmentsOpen section

Let's learn

A virtual environment is an isolated Python installation for a specific project. Each project gets its own set of packages, so Project A can use requests==2.28 while Project B uses requests==2.31.

bash

python -m venv venv         # Create virtual environment
source venv/bin/activate    # Activate (macOS/Linux)
venv\Scripts\activate       # Activate (Windows)
pip install requests        # Install in this environment only
deactivate                  # Deactivate when done

We'll cover virtual environments in depth in Chapter 7. For now, just know they exist.

VS Code + Python ExtensionOpen section

Let's learn

VS Code is a free, open-source code editor by Microsoft. The Python extension adds:

Syntax highlighting — Colors for keywords, strings, comments
IntelliSense — Autocomplete as you type
Debugging — Set breakpoints, step through code
Linting — Catch errors before running
Formatting — Auto-format on save
Integrated terminal — Run Python without leaving VS Code

Other editors work (PyCharm, Sublime Text, Vim), but VS Code is the most popular for Python development.

Mental model: The Python toolchain

Think of the Python toolchain like a kitchen:

Python interpreter = The chef (reads and executes your recipes)
pip = The pantry delivery service (brings ingredients from PyPI)
Virtual environment = Your own kitchen (isolate your ingredients)
VS Code = The recipe editor (write and test your recipes)

Installing Python on Windows

Step 1: Download the installer

Go to python.org/downloads and click the big yellow "Download Python 3.12.x" . This downloads the installer for the latest stable version.

Step 2: Run the installer

Double-click the downloaded file. You'll see a screen with checkboxes at the bottom. This is the most important step:

✅ Check "Add Python.exe to PATH" (or "Add Python 3.12 to PATH")

If you skip this, you'll have to manually edit your system PATH later. Don't skip it.

Then click "Install Now" (not "Customize installation" — the defaults are fine).

Step 3: Verify the installation

Open a terminal:

Press Win + R, type cmd, press Enter
Or search for "Command Prompt" in the Start menu

In the terminal, run:

bash

python --version

You should see something like Python 3.12.0. If you do, you're done.

The py launcher

Windows also installs the py launcher, which lets you run Python with py instead of python. This is useful if you have multiple Python versions installed:

bash

py --version
py -3.12 script.py  # Run with Python 3.12 specifically

For this course, use python (not py) to stay consistent with macOS/Linux. But know that py exists.

Installing Python on macOS

macOS used to ship with Python 2.7 pre-installed, but that's gone in recent versions. You need to install Python 3 yourself.

Option A: python.org installer (recommended for beginners)

Go to python.org/downloads and download the macOS installer (a .pkg file). Double-click it and follow the prompts.

After installation, open Terminal and run:

bash

python3 --version

Note: on macOS, the command is python3, not python. The python command might still point to Python 2 (if it exists at all).

Option B: Homebrew (for developers who use Homebrew)

If you already use Homebrew, you can install Python with:

bash

brew install python

This installs Python 3 and makes it available as python3.

Verify the installation

bash

python3 --version

You should see Python 3.12.0 or similar.

Installing Python on Linux

Most Linux distributions ship with Python 3 pre-installed. Check with:

bash

python3 --version

If you see Python 3.8 or newer, you're good. If you need a newer version (3.12+), use your package manager:

Ubuntu/Debian:

bash

sudo apt update
sudo apt install python3.12 python3.12-venv

Fedora:

bash

sudo dnf install python3.12

Arch:

bash

sudo pacman -S python

After installation, verify with python3 --version.

The REPL: your first Python command

Once Python is installed, you can use the REPL (Read-Eval-Print Loop), an interactive shell where you can type Python code and see the results immediately.

Open a terminal and run:

bash

python    # Windows
python3   # macOS/Linux

You'll see a prompt like >>>. This is the REPL. Type Python code and press Enter:

python

>>> 2 + 2
4
>>> print("Hello, world!")
Hello, world!
>>> exit()

The REPL is your scratchpad for experimenting. You'll use it throughout this course.

To exit the REPL, type exit() or press Ctrl+D (macOS/Linux) or Ctrl+Z then Enter (Windows).

VS Code setup

VS Code is the most popular editor for Python. It's free, fast, and has excellent Python support.

Step 1: Install VS Code

Download from code.visualstudio.com and install it.

Step 2: Install the Python extension

Open VS Code
Click the Extensions icon in the left sidebar (or press Ctrl+Shift+X)
Search for "Python"
Install the extension by Microsoft (it's the one with the most downloads)

Step 3: Select the Python interpreter

Open a Python file (or create one: File → New File → test.py)
Press Ctrl+Shift+P (or Cmd+Shift+P on macOS) to open the Command Palette
Type "Python: Select Interpreter" and press Enter
Choose the Python 3.12+ interpreter you installed

VS Code will now use that interpreter to run your code and provide autocomplete.

Step 4: Configure settings

Open Settings (Ctrl+, or Cmd+,) and search for "Python". Set:

Editor: Format On Save → ✅ (keeps your code clean)
Python > Analysis: Type Checking Mode → "basic" (catches type errors)
Editor: Tab Size → 4 (Python's standard indentation)

Step 5: Install a theme (optional)

A good theme makes code easier to read. Popular choices:

One Dark Pro (dark)
GitHub Light (light)
Dracula (dark, high contrast)

Install from the Extensions tab.

Terminal basics

You'll use the terminal a lot in Python development. Here are the commands you need:

Navigate directories:

bash

cd folder_name      # Go into a folder
cd ..               # Go up one level
pwd                 # Print current directory (macOS/Linux)
cd                  # Print current directory (Windows, use 'cd' alone)

List files:

bash

ls                  # List files (macOS/Linux)
dir                 # List files (Windows)

Run Python:

bash

python script.py    # Run a Python file (Windows)
python3 script.py   # Run a Python file (macOS/Linux)

Create a folder:

bash

mkdir folder_name   # Create a folder

Open VS Code from terminal:

bash

code .              # Open current folder in VS Code

Common mistakes

Mistake	Why it's wrong	Fix
`python` command not found on Windows	Python isn't in your PATH	Re-run the installer and check "Add Python to PATH", or manually add `C:\Users\<YourName>\AppData\Local\Programs\Python\Python312` to your PATH
`python` opens Microsoft Store on Windows	Windows 10/11 has an alias that redirects `python` to the Store	Go to Settings → Apps → App execution aliases → Turn off "python.exe" and "python3.exe" aliases
`python` works but `python3` doesn't (or vice versa)	Different OS conventions: Windows uses `python`, macOS/Linux use `python3`	Use the command for your OS. If you need both, create an alias or use `py -3` on Windows
VS Code shows "Python not installed" even though it is	VS Code can't find the interpreter	Open Command Palette → "Python: Select Interpreter" → choose the correct path
`SyntaxError` when running a Python 2 tutorial	Python 2 syntax (`print "hello"`) doesn't work in Python 3	Use Python 3 syntax: with parentheses

Production notes

expected

Hello from VS Code!

Write your solutionCtrl+Enter to run

Ctrl+Enter

Interview Questions

Beginner:

"What's the difference between python and python3?"

python is the command on Windows; python3 is the command on macOS/Linux. Both run Python 3. On Windows, python3 might not exist (or might open the Microsoft Store). On macOS/Linux, python might point to Python 2 (if it exists at all).
"What is the Python REPL?"

The REPL (Read-Eval-Print Loop) is an interactive shell where you can type Python code and see the results immediately. You start it by running python (Windows) or python3 (macOS/Linux) in the terminal. It's useful for experimenting and testing small snippets.

Senior:

"Why is it important to add Python to your PATH during installation?"

The PATH is a list of directories your system searches when you type a command. If Python isn't in your PATH, the terminal can't find the executable, and you'll get "command not found". Adding Python to PATH lets you run from any directory.

Summary

Install Python 3.12+ from python.org (Windows/macOS) or your package manager (Linux).
On Windows, check "Add Python to PATH" during installation.
Use python on Windows, python3 on macOS/Linux.
The REPL is your interactive scratchpad for experimenting.
VS Code + Python extension is the standard setup. Configure format-on-save and tab size 4.
Common mistakes: PATH issues, Microsoft Store alias, using python vs python3.

Quick recall

text

I want to…
├── Install Python → python.org/downloads (Windows/macOS) or apt/brew (Linux)
├── Run Python → python (Windows) or python3 (macOS/Linux)
├── Open the REPL → python or python3 in terminal
├── Run a script → python script.py or python3 script.py
├── Select interpreter in VS Code → Ctrl+Shift+P → "Python: Select Interpreter"
└── Fix "command not found" → Add Python to PATH (Windows) or use python3 (macOS/Linux)

Self-Check Quiz

Q1 / 3

MCQ

What's the most important checkbox during Python installation on Windows?

Chapter 2 — Installing Python & VS Code

The why

Core concepts: What you're installing

Installing Python on Windows

Installing Python on macOS

Installing Python on Linux

The REPL: your first Python command

VS Code setup

Terminal basics

Common mistakes

Production notes

Practice: Prove your Mastery

Check Python Version

REPL Exploration

Run a Script File

VS Code Interpreter

VS Code Run

Interview Questions

Summary

Quick recall

Self-Check Quiz