homepage

The XDG standard seems to focus on desktop GUI applications and that's also where it's mostly used. Python has it's own installation scheme, which is documented at the top of sysconfig.py and which we've had ever since distutils became part of the stdlib.
For user installs, this bases all installations under the PYTHONUSERBASE dir, which defaults to ~/.local/ on Unix.
So user installs go into ~/.local/pythonX.X/ (I also have a ~/.local/python/X.X/ - not sure where that came from).
Python also uses ~/.pypirc for PyPI, ~/.python-eggs for setuptools, ~/.python_history for readline history.
The installation scheme currently doesn't define a dir for config files, only for "data" files, so adding one would probably be wise.
Since we already own ~/.local/pythonX.X/, why not put config files in there ?
For some extra Unix touch, we could use ~/.local/pythonX.X/etc/ and then move the cache bits to a ./var/ subdir (by defining another new "cache" entry for the schemes).