Python Setup & Environment

Why Setup Matters

A proper Python setup is the foundation for all Python development. Without it, you'll run into dependency conflicts, version issues, and frustrating debugging sessions.

Installing on Different Platforms

Windows:

1. Download from python.org
2. Run the installer with "Add Python to PATH" checked
3. Verify installation:

python --version
# Python 3.12.0

pip --version
# pip 23.3.1 from ... (python 3.12)

macOS:

# Using Homebrew (recommended)
brew install python@3.12

# Verify
python3 --version

Linux (Ubuntu/Debian):

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

# Verify
python3 --version

Common Installation Issues

Why Virtual Environments?

Virtual environments isolate project dependencies. Without them:

• Project A needs requests==2.28
• Project B needs requests==2.31
• Conflict!

Creating Virtual Environments

# Create a virtual environment
python -m venv myenv

# Activate it
# Windows
myenv\Scripts\activate

# macOS/Linux
source myenv/bin/activate

# You'll see (myenv) in your prompt
(myenv) $ 

Managing Dependencies

# Install packages
pip install requests flask

# Save dependencies
pip freeze > requirements.txt

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

# Deactivate when done
deactivate

Best Practices

1. Always use virtual environments - never install globally
2. Add .env to .gitignore - never commit virtual environments
3. Use requirements.txt - document your dependencies
4. Name environments clearly - myenv is not descriptive

Modern Alternatives

# Using poetry (modern dependency management)
poetry new myproject
cd myproject
poetry add requests

# Using pipenv
pipenv install requests

Interactive Mode (REPL)

$ python3
>>> 2 + 2
4
>>> print('Hello, World!')
Hello, World!
>>> exit()

Use the REPL for:

• Quick experiments
• Testing small code snippets
• Learning new features

Running Scripts

# hello.py
def greet(name):
    return f'Hello, {name}!'

if __name__ == '__main__':
    print(greet('World'))

$ python hello.py
Hello, World!

The if __name__ == '__main__' Pattern

This pattern ensures code runs only when executed directly (not when imported):

# utils.py
def add(a, b):
    return a + b

# This only runs when utils.py is executed directly
if __name__ == '__main__':
    print(add(2, 3))  # 5

Running Python One-Liners

# Using -c flag
$ python -c "print('Hello')"
Hello

# Using python -m to run modules
$ python -m http.server 8000
# Starts a simple HTTP server

IDE Setup

VS Code:

1. Install Python extension
2. Select Python interpreter
3. Use built-in terminal

PyCharm:

1. Create new project
2. Auto-detects virtual environment
3. Full debugging support