On Thu, Jun 25, 2020 at 12:37 AM Paul Moore firstname.lastname@example.org wrote:
I think the key message here is that you won't be re-inventing the wheel. This is a wheel that still needs to be invented.
It _was_ invented, but it is off round and gives a rough ride. As noted in the first post this:
__requires__ = ['scipy <1.3.0,>=1.2.0', 'anndata <0.6.20', 'loompy
<3.0.0,>=2.00', 'h5py <2.10'] import pkg_resources
was able to load the desired set of package-versions for scanpy, but setting a version number constraint on scanpy itself at the end of that list, one which matched the version that the preceding commands successfully loaded, broke it. So it is not reliable.
And the entire __requires__ kludge is only present because for reasons beyond my pay grade this:
import pkg_resources pkg_resources.require("scipy<1.3.0,>=1.2.0;anndata<0.6.20;etc.") import scipy import anndata
cannot work because by default "import pkg_resources" keeps only the most recent version rather than making up a tree (or list or hash or whatever) and waiting to see if there are any version constraints to be applied at the time of actual package import.
What I'm doing now is basically duct tape and bailing wire to work around those deeper issues. In terms of language design, a much better fix would be to modify pkg_resources so that it will always successfully load the required versions from a designated directory which contains multiple versions of packages, and modify the package maintenance tools so that they can maintain such a directory.