What problem does it solve? Writing small macOS utilities often pulls in Homebrew, pip, or virtual environments that break on clean machines. This Skill constrains scripts to Apple's /usr/bin/python3 and the Python 3.9 standard library so they run on any Mac with Command Line Tools installed. ## Core Features & Use Cases - Zero-dependency scripting: Enforces the #!/usr/bin/python3 shebang, Python 3.9 syntax (Optional/Union instead of T | None), and standard-library-only imports such as argparse, json, plistlib, pathlib, and subprocess. - Safe macOS integration: Invokes stable system programs via absolute paths and argument arrays, never shell=True, with typed functions and isinstance narrowing of decoded plist/JSON data. - Isolated verification: Validates scripts with /usr/bin/python3 -E -s -S and runs tests via unittest discover without environment leakage. - Use Case: Build a CLI tool that reads a plist preference file, opens a URL with /usr/bin/open, and exits with a clean error message — all without installing anything on the target Mac. ## Quick Start Write a macOS utility script that runs on Apple's /usr/bin/python3 using only the standard library to parse a plist file and print selected keys.
