It would appear that Python 3.x is trying to use the 2.x version of Pygame which, as you saw, will never end well given the significant changes between 2.x and 3.x.

The Pygame website suggests that it is mostly compatible with Python 3.x. However, it says you'll have to "copy and paste" files to make it work (see here). As to what that means is a bit of a mystery but I'm guessing that this means you'll have to copy the libraries from the 2.x site-packages folder to the 3.x one.

I'm guessing Pygame will only work with a package manager (like MacPorts) if your whole Python workflow was built with MacPorts. In other words, the MacPorts pygame will work with a MacPorts compiled Python. If you're trying to use a MP Pygame with an official Python installation (or the system one), you'll probably run into trouble.