Python Getting Started

Python Getting Started: Environment Setup & Script Execution

To begin development with Python, you need a working Python 3 runtime and an isolated project environment. Managing dependencies cleanly from day one prevents package collisions across projects.

Developer Tooling Lifecycle

flowchart TD
    A["Install Python 3 Runtime"] --> B["Create Virtual Environment (venv)"]
    B --> C["Activate Virtual Environment"]
    C --> D["Install Packages via pip"]
    D --> E["Execute Script via Terminal"]

Setting Up a Virtual Environment

Always create a local venv directory inside your project root to isolate installed packages:

# Initialize virtual environment
python -m venv .venv

# Activate on Linux / macOS
source .venv/bin/activate

# Activate on Windows (PowerShell)
.venv\Scripts\Activate.ps1

Practical Code Example

import sys
from pathlib import Path

def verify_environment() -> None:
    """Check if the script is running inside a virtual environment."""
    executable_path = Path(sys.executable)
    in_venv = sys.prefix != sys.base_prefix
    
    print(f"Python Interpreter Path: {executable_path}")
    print(f"Virtual Environment Active: {in_venv}")
    
    if not in_venv:
        print("Warning: Running globally! Consider activating a virtual environment (.venv).")

if __name__ == "__main__":
    verify_environment()

Best Practices & Gotchas

• Never Install Packages Globally: Avoid running pip install outside an active virtual environment to keep your system Python clean.
• Use .gitignore for .venv: Never check .venv or __pycache__ directories into version control.
• Specify Entry Points cleanly: Guard standalone script logic with if __name__ == '__main__': to ensure modules can be imported safely without executing side effects.

Self-Check Challenge

Create a virtual environment, activate it, write a Python script named check_env.py that verifies sys.prefix, and verify that in_venv evaluates to True.