Sigh. I have the same problem; tried using XCode as my developement environment for my master's class. Too many of the repliers fail to realize that python 3 is installed in a different place (library/frameworks/...) now than the older usr/bin location for 2.7. And that's by the official installer from the python org website. I tried doing it by Homebrew so it would go in the 'normal' place, but Homebrew would only install an older version of python3 versus the listed current version, so I dumped it all (My class was based on the lastest version of python, so I didn't want to run into code incompatibility issues).Frustrated with the entire ordeal, I scrapped it. Switched back and forth between using BBEdit for editing the python scripts or the basic IDLE environment included with the app (BBEdit can't run interactive programs requiring user input, but it's fine for simple scripts).it's a shame none of these 'master's' have a better answer.