To help you get your media center running smoothly, let me know: What are you currently running? What is the exact error message you see on your screen? Which add-on or skin are you trying to install?
While there's no standalone Python 3 ZIP file to download, there are plenty of resources available for developers: xbmc python 30 0 zip download free
Always the best source for stable, Python 3-compliant add-ons. To help you get your media center running