It would be nice to settle this.

Personally I would like to see the defaults being:

Linux: ~/.pythonx.y
Mac OS X: ~/.pythonx.y with a fallback of ~/Library/Preferences/.pythonx.y
Windows: ~/pythonx.y perhaps with a backup of AppData/pythonx.y

For both Windows and Mac OS X I would be happy with the fallback / primary to be the other way round - it doesn't *really* matter. The API for getting the user config direction should always return a list I guess if we have fallbacks.

Someone else in the Python-dev discussion thread (Adal Chiriliuc) expressed a preferences for the documents folder on Windows over the home directory. This would be fine as well (with AppData still as a fallback). This is used by other native windows applications. (In earlier versions of Windows the documents folder was explicitly called "Documents and Settings".)

We should use pythonx.y rather than just python because (for example) you will typically have different packages installed when you have multiple versions of Python, and in unittest would then want / need different plugins enabled and configured in the unittest config files for each of the versions of Python.