> I thought the whole objection to data_files was that it allows python package installations to stick files in arbitrary places, i.e. do stuff that should be the sole preserve of the system package manager.
But those "arbitrary places" include things like the standard places where man pages and other documentation go, the standard places where shared data (and things like example programs) go, etc. Without data_files the Python installation tools give you no way to provide any of these things with your Python library.
Man-pages is a Linux thing, while python packages are cross-platform and can be installed on Windows.
It seems out of scope for a python packager to include such files. As a user i would also not be very happy to see a pip install start dropping files all over my system. How would that behave in a virtualenv anyway? Sandboxing should be a key feature of a package manager.
> Man-pages is a Linux thing, while python packages are cross-platform and can be installed on Windows.
Windows has help files, which are its version of man pages. So an installer that installed man pages on Linux would be expected to install the corresponding help files on Windows.
> dropping files all over my system
I said no such thing. I said there are certain designated places in a filesystem where certain common items like man pages (or Windows help files) live. Not to mention system-wide configuration files (which on Linux go in /etc), and I'm sure there are others I've missed. An installer that is not allowed to access those places does not seem to me to be a complete installer. Linux package manager installers certainly put files in such places. Windows installers do it too (although the specific items and places are different).
> How would that behave in a virtualenv anyway?
A complete virtualenv would have its own copies of the above types of files, in the appropriate places relative to the root of the virtualenv.
But those "arbitrary places" include things like the standard places where man pages and other documentation go, the standard places where shared data (and things like example programs) go, etc. Without data_files the Python installation tools give you no way to provide any of these things with your Python library.