00.2 - Setting Up Your Python Development Environment

Theory 20 min Beginner

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Development Environment Overview

A Python development environment consists of three components:

┌─────────────────────────────────────────────────────────────┐
│              Python Dev Environment                          │
│                                                             │
│  ┌──────────────┐   ┌─────────────────┐   ┌─────────────┐  │
│  │   Python 3   │   │   VS Code IDE   │   │  Terminal   │  │
│  │  Interpreter │   │  + Extensions   │   │  (bash/zsh/ │  │
│  │  (CPython)   │   │                 │   │  PowerShell)│  │
│  └──────────────┘   └─────────────────┘   └─────────────┘  │
│         ▲                   ▲                   ▲           │
│         └───────────────────┴───────────────────┘          │
│                   Your Python Project                        │
└─────────────────────────────────────────────────────────────┘

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Step 1 — Install Python 3

Windows

1. Go to https://www.python.org/downloads/
2. Download the latest Python 3.x installer
3. Important: Check ✅ "Add Python to PATH" before clicking Install
4. Click "Install Now"

Verify:

python --version
# Python 3.11.x
pip --version
# pip 23.x from ...

macOS

# Using Homebrew (recommended)
brew install python3

python3 --version
pip3 --version

Linux (Ubuntu/Debian)

sudo apt update
sudo apt install python3 python3-pip python3-venv

python3 --version

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Step 2 — Install VS Code

1. Download from https://code.visualstudio.com/
2. Install the Python extension by Microsoft:
   • Open VS Code → Ctrl+Shift+X (Extensions)
   • Search "Python" → Install the Microsoft extension

Recommended VS Code Extensions for Python

Extension	Purpose
Python (Microsoft)	IntelliSense, debugging, linting
Pylance	Fast type checking and autocompletion
Ruff	Ultra-fast linter (replaces flake8)
Black Formatter	Auto-format code on save
Jupyter	Run notebooks inside VS Code
GitLens	Git integration

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Step 3 — Configure VS Code for Python

Press Ctrl+Shift+P and type "Python: Select Interpreter" to choose your Python version.

Add these to your VS Code settings.json (Ctrl+Shift+P → "Open User Settings JSON"):

{
  "[python]": {
    "editor.defaultFormatter": "ms-python.black-formatter",
    "editor.formatOnSave": true
  },
  "python.analysis.typeCheckingMode": "basic",
  "editor.rulers": [88]
}

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Step 4 — The Python REPL

The REPL (Read-Eval-Print Loop) is the interactive Python shell — perfect for experimenting.

# Launch the REPL
# In terminal: python3

>>> print("Hello, World!")
Hello, World!

>>> 2 + 3
5

>>> name = "Python"
>>> f"Hello, {name}!"
'Hello, Python!'

>>> exit()

REPL command	Purpose
python3	Start the REPL
exit() or Ctrl+D	Exit
_	Last result (>>> 2+2 then >>> _ gives 4)
help(str)	Get documentation on any object
dir(list)	List all methods of an object

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Step 5 — Your First Python Script

Create a file hello.py:

# hello.py — My first Python script

name = input("What is your name? ")
age = int(input("How old are you? "))

print(f"Hello, {name}!")
print(f"In 10 years, you will be {age + 10} years old.")

Run it:

python3 hello.py
# What is your name? Alice
# How old are you? 25
# Hello, Alice!
# In 10 years, you will be 35 years old.

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Virtual Environments (Preview)

A virtual environment isolates your project's packages from the global Python installation. You'll learn the full details in Module 06, but here's a quick preview:

# Create a virtual environment
python3 -m venv venv

# Activate it (macOS/Linux)
source venv/bin/activate

# Activate it (Windows)
venv\Scripts\activate

# Install packages (isolated)
pip install requests

# Deactivate
deactivate

Rule: Always use a virtual environment for every project.

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Python Code Structure

#!/usr/bin/env python3
"""
Module docstring: brief description of this file.
"""

# 1. Standard library imports
import os
import sys

# 2. Third-party imports
import requests

# 3. Local imports
# from mymodule import myfunction

# 4. Constants
MAX_RETRIES = 3

# 5. Functions and classes
def main():
    """Entry point of the script."""
    print("Hello from main!")

# 6. Entry point guard
if __name__ == "__main__":
    main()

The if __name__ == "__main__": guard ensures main() only runs when the script is executed directly, not when it's imported as a module.

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Key Vocabulary

Term	Definition
Interpreter	The program that reads and executes Python code (python3)
REPL	Interactive shell: type Python, get immediate results
Script	A .py file containing Python code
IDE	Integrated Development Environment (VS Code, PyCharm)
Extension	Plugin that adds functionality to VS Code
Virtual environment	Isolated Python installation for a single project
__name__	Special variable: "__main__" when run directly, module name when imported
Shebang	#!/usr/bin/env python3 — tells the OS which interpreter to use

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Summary

• Python 3.10+ is required — always add Python to PATH during installation
• VS Code with the Python + Pylance + Black extensions is the recommended setup
• The REPL (python3) lets you test code interactively
• Use if __name__ == "__main__": as the entry point in every script
• Virtual environments isolate project dependencies — always use them

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📄️ 00.1 - Why Python?

Understand Python's origins, what makes it unique, and where it fits in today's technology landscape

📄️ 00.2 - Setup Your Environment

Install Python 3, configure VS Code with extensions, understand the REPL, and create your first script

📄️ Lab - Module 00

Install Python 3, configure VS Code, use the REPL, and write an interactive CLI script

📄️ Quiz - Module 00

30 interactive questions to validate your understanding of Python history, setup, and ecosystem