Installing my sdist from PyPI puts the files in unexpected places

The data_files parameter is for data files who isn't a part of the package. You should probably use package_data instead.

See https://docs.python.org/3/distutils/setupscript.html#installing-package-data

That wouldn't install the data in site-packages/data, but in my opinion that's not where is should be installed anyway. You won't know which package it's a part of. It should be installed in site-packages//gloopy-0.1.alpha-py2.7.egg/[data|doc|examples] IMO.

If you really do think the data is not package data, then you should use data_files and in that case pip installs it correctly, while I'd claim setup.py install installs it in the wrong place. But in my opinion, in this case, it is package_data, as it's related to the package, and not used by other software.