Chapter 1: Setting Up Python - BlackArmorAI LMS: CS with Python & System Design Thinking Development

Overview

Setting up a proper Python development environment is the foundation for building scalable applications. This chapter covers everything you need to get started with Python development on both macOS and Windows, including environment setup, essential tools, and best practices for project organization.

You'll learn how to install Python, set up virtual environments, configure your development tools, and establish a workflow that supports scalable application development. These skills are essential for any Python developer working on system design and full-stack applications.

What You'll Learn:

Python installation and configuration
Virtual environment management
Development tool setup
Project structure and organization
Package management with pip
IDE and editor configuration

Python Environment Setup Workflow

Python Development Environment Components

Component	Purpose	Installation Method	Configuration	Verification
Python Interpreter	Core runtime environment	Official installer, pyenv	PATH environment variable	python --version
Package Manager (pip)	Install Python packages	Included with Python	pip.conf, requirements.txt	pip --version
Virtual Environment	Isolate project dependencies	venv, virtualenv	Activation scripts	which python
Code Editor/IDE	Development interface	VS Code, PyCharm	Extensions, themes	Feature testing
Version Control	Code management	Git installer	User config, SSH keys	git --version

Python Environment Setup Process

graph TD A[Download Python] --> B[Install Python] B --> C[Verify Installation] C --> D[Install pip] D --> E[Create Virtual Environment] E --> F[Activate Environment] F --> G[Install Dependencies] G --> H[Configure IDE] H --> I[Set up Git] I --> J[Create Project Structure] J --> K[Install Development Tools] K --> L[Verify Setup] C --> M{Installation Success?} M -->|No| N[Troubleshoot] N --> B M -->|Yes| D L --> O{Setup Complete?} O -->|No| P[Fix Issues] P --> L O -->|Yes| Q[Start Development] style A fill:#e1f5fe style B fill:#f3e5f5 style C fill:#e8f5e8 style D fill:#fff3e0 style E fill:#fce4ec style F fill:#e0f2f1 style G fill:#f1f8e9 style H fill:#e8eaf6 style I fill:#fafafa style J fill:#fff8e1 style K fill:#f3e5f5 style L fill:#e8f5e8 style Q fill:#c8e6c9

Key Environment Variables & Configuration

PYTHONPATH

/usr/local/bin/python3:/usr/bin/python3

Specifies additional directories to search for Python modules. Controls module import behavior and package discovery.

Python PATH Documentation →

VIRTUAL_ENV

/path/to/venv

Points to the active virtual environment directory. Used by Python to identify the current virtual environment.

Virtual Environment Documentation →

PIP_CONFIG_FILE

~/.pip/pip.conf

Location of pip configuration file. Defines package sources, user settings, and installation preferences.

Pip Configuration →

PYTHONSTARTUP

~/.pythonrc

Path to Python startup file executed when Python starts. Used for custom initialization and imports.

Python Startup Documentation →

PYTHONUNBUFFERED

1

Forces stdout and stderr to be unbuffered. Essential for real-time logging in containerized environments.

Python Unbuffered Documentation →

PYTHONDONTWRITEBYTECODE

1

Prevents Python from writing .pyc files. Useful for development environments to avoid cache issues.

Python Bytecode Documentation →

Critical Configurations

Python Version

Python 3.12+ (latest stable)
pip package manager
venv module for virtual environments

Development Tools

Git for version control
VS Code or Cursor IDE
Terminal/Command Prompt

Essential Packages

Flask for web development
SQLAlchemy for database ORM
pytest for testing

Mac Setup

Installing Python on macOS

macOS comes with Python 2.7 pre-installed, but we need Python 3.x for modern development. Here's how to set it up properly:

Using Homebrew (Recommended)

# Install Homebrew if you don't have it
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# Install Python 3.12
brew install python@3.12

# Verify installation
python3 --version
pip3 --version

Homebrew is the preferred package manager for macOS. It handles dependencies and updates automatically.

Configuring PATH

Ensure Python is in your PATH by adding it to your shell configuration:

For Zsh (macOS Catalina+)

# Add to ~/.zshrc
echo 'export PATH="/opt/homebrew/bin:$PATH"' >> ~/.zshrc
echo 'export PATH="/opt/homebrew/opt/python@3.12/bin:$PATH"' >> ~/.zshrc

# Reload configuration
source ~/.zshrc

Alternative: Official Python Installer

If you prefer not to use Homebrew, you can download the official installer from python.org:

Steps for Official Installer

Visit python.org/downloads
Download Python 3.12.x for macOS
Run the installer package
Check "Add Python to PATH" during installation
Verify installation in Terminal

Windows Setup

Installing Python on Windows

Windows doesn't come with Python pre-installed, so we'll need to install it manually:

Using Official Installer

# After installation, verify in Command Prompt
python --version
pip --version

# If python command doesn't work, try:
py --version
py -m pip --version

The Windows installer includes pip and adds Python to your PATH automatically.

Windows Subsystem for Linux (WSL)

For a more Unix-like experience on Windows, consider using WSL:

Installing WSL

# Enable WSL feature
dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart

# Install Ubuntu from Microsoft Store
# Then in Ubuntu terminal:
sudo apt update
sudo apt install python3 python3-pip python3-venv

Using Chocolatey Package Manager

Chocolatey is a package manager for Windows that makes installation easier:

Installing with Chocolatey

# Install Chocolatey first (run as Administrator)
Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1'))

# Install Python
choco install python

# Verify installation
python --version

Virtual Environments

Virtual environments are crucial for isolating project dependencies and avoiding conflicts between different projects.

Creating and Using Virtual Environments

# Create a new virtual environment
python3 -m venv myproject

# Activate the virtual environment
# On macOS/Linux:
source myproject/bin/activate

# On Windows:
myproject\Scripts\activate

# Your prompt should change to show the environment name
(myproject) $

# Install packages in the virtual environment
pip install flask sqlalchemy

# Deactivate when done
deactivate

Virtual environments create isolated Python environments where you can install packages without affecting your system Python.

Managing Dependencies

Keep track of your project dependencies:

Requirements File

# Generate requirements.txt
pip freeze > requirements.txt

# Install from requirements.txt
pip install -r requirements.txt

Best Practices for Virtual Environments

Create one virtual environment per project
Always activate the environment before working
Keep requirements.txt updated
Don't commit virtual environment folders to Git
Use descriptive environment names

Essential Packages

These packages form the foundation of modern Python web development:

Core Development Packages

# Activate your virtual environment first
source myproject/bin/activate

# Web Framework
pip install flask

# Database ORM
pip install sqlalchemy flask-sqlalchemy

# HTTP requests
pip install requests

# Testing framework
pip install pytest

# Environment variables
pip install python-dotenv

# Database migrations
pip install flask-migrate

# User authentication
pip install flask-login

# Verify installations
pip list

Flask Ecosystem

Flask: Core web framework
Flask-SQLAlchemy: Database integration
Flask-Login: User authentication
Flask-Migrate: Database migrations

Development Tools

pytest: Testing framework
python-dotenv: Environment management
requests: HTTP client
black: Code formatting

Code Editors

VS Code (Visual Studio Code)

VS Code is a popular, free code editor with excellent Python support:

VS Code Setup

Download and install VS Code from code.visualstudio.com
Install the Python extension (Microsoft)
Install the Python IntelliSense extension
Configure your Python interpreter

Cursor (AI-Powered Editor)

Cursor is built on VS Code but includes AI assistance:

Cursor Features

AI code completion and generation
Built-in chat interface
Code explanation and documentation
Bug detection and fixes

PyCharm (Professional IDE)

PyCharm is a full-featured Python IDE with advanced features:

PyCharm Benefits

Advanced debugging tools
Database integration
Built-in testing tools
Refactoring support

Python Development Environment Setup Process

Environment Configuration Dataset

Component	Version	Installation Method	Configuration File	Status
Python	3.12.0	Homebrew/Installer	~/.zshrc	✅ Required
Virtual Environment	venv	Built-in	requirements.txt	✅ Required
Flask	3.0.0	pip install	app.py	✅ Required
SQLAlchemy	2.0.23	pip install	models.py	✅ Required
pytest	7.4.3	pip install	tests/	✅ Required
VS Code/Cursor	Latest	Download	settings.json	✅ Recommended

Development Environment Setup Flow

flowchart TD A[Start: System Check] --> B{OS Detection} B -->|macOS| C[Install Homebrew] B -->|Windows| D[Download Python Installer] B -->|Linux| E[Use Package Manager] C --> F[Install Python 3.12] D --> F E --> F F --> G[Verify Installation] G --> H{Installation Success?} H -->|No| I[Debug Installation] I --> F H -->|Yes| J[Configure PATH] J --> K[Create Project Directory] K --> L[Initialize Virtual Environment] L --> M[Activate Environment] M --> N[Install Core Packages] N --> O[Flask Installation] N --> P[SQLAlchemy Installation] N --> Q[pytest Installation] O --> R[Configure IDE] P --> R Q --> R R --> S[Create Basic Flask App] S --> T[Test Application] T --> U{App Working?} U -->|No| V[Debug Issues] V --> S U -->|Yes| W[Environment Ready!] style A fill:#e1f5fe style W fill:#c8e6c9 style H fill:#ffecb3 style U fill:#ffecb3

Environment Variables & Configuration

PATH Configuration

export PATH="/opt/homebrew/bin:$PATH"

Adds Homebrew binaries to system PATH for macOS

📖 Python macOS Guide

Python Version

python3 --version

Verifies Python 3.12+ installation

📖 Python Downloads

Virtual Environment

python3 -m venv myproject

Creates isolated Python environment

📖 venv Documentation

Package Installation

pip install flask sqlalchemy pytest

Installs core development packages

📖 pip Documentation

Flask Configuration

app.config['SECRET_KEY'] = 'your-secret-key'

Sets Flask application secret key

📖 Flask Configuration

Database URI

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'

Configures SQLAlchemy database connection

📖 Flask-SQLAlchemy Config

Hands-On Exercise: Your First Flask App

Building a Simple Flask Application

Beginner

Objective

Create a simple Flask web application to verify your Python setup and learn basic Flask concepts.

Steps

Set up your development environment
Create a new project directory
Set up a virtual environment
Install Flask
Create a simple Flask application
Run and test the application

Complete Implementation

# app.py
from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/')
def home():
    return jsonify({
        "message": "Hello, Python is working!",
        "status": "success",
        "framework": "Flask"
    })

@app.route('/health')
def health():
    return jsonify({
        "status": "healthy",
        "message": "Flask is running"
    })

if __name__ == '__main__':
    app.run(debug=True, host='0.0.0.0', port=5000)

Running the Application

# Create project directory
mkdir my-first-flask-app
cd my-first-flask-app

# Create virtual environment
python3 -m venv venv

# Activate virtual environment
source venv/bin/activate  # On Windows: venv\Scripts\activate

# Install Flask
pip install flask

# Create app.py with the code above
# Then run:
python app.py

Testing

Open your browser and visit:

http://localhost:5000/ - Main endpoint
http://localhost:5000/health - Health check

Key Takeaways

🐍

Python Installation

Always use Python 3.x for new projects. Use package managers like Homebrew (Mac) or Chocolatey (Windows) for easier installation and updates.

🔒

Virtual Environments

Use virtual environments for every project to isolate dependencies and avoid conflicts between different projects.

📦

Package Management

Keep requirements.txt updated and use pip for package management. Consider using pip-tools for more advanced dependency management.

⚙️

Development Tools

Choose a code editor that fits your workflow. VS Code and Cursor are excellent choices for Python development.

Next Steps

Preparation for Chapter 2

Before moving to the next chapter, practice:

Create multiple virtual environments for different projects
Install and test different packages
Modify the Flask app to add new routes
Experiment with different code editors
Set up Git for version control

Cross-References

Related Chapters

External Resources

Conclusion

You now have a solid Python development environment set up on your machine. This foundation will serve you well as we move into more advanced topics like AI-assisted development, database design, and system architecture.

Remember: A well-configured environment saves time and prevents "it works on my machine" problems that can frustrate both you and your teammates.