Today in #debian-python we discussed bug #695707, which describes a breakage in virtualenv with Python 2.7 in experimental due to multiarch. We explored a few approaches for fixing this, centered around patching virtualenv itself, but none of the solutions (including the one in PAPT svn :/ ) are entirely satisfying. Stefano made the observation that you really want the multiarch triplet that Python was built with, not necessarily the triplet on the host platform its installed on, which makes sense to my limited exposure to multiarch. In any case, fixing this in virtualenv is both problematic and rather shortsighted, since this problem keeps coming up again and again in other packages. The other complication is that you generally have to shell-out to get the right value, calling one of the following commands: $ dpkg-architecture -qDEB_BUILD_MULTIARCH $ gcc --print-multiarch Stefano brought up the inefficiencies of doing this in virtualenv's site.py every time you fire up your venv Python. Doko suggested globbing sys.path entries, but that seems error-prone, and someone else seemed to remember cases where this was tried and didn't work very well. Wouldn't it be nice if Python just told you what the values were? We could calculate this once during Python's build, and now all Python code just gets it for free with a simple import. In Python 3.3 (and beyond) we have the perfect place to stash this information. PEP 421's sys.implementation allows for platform-specific values, so we can squirrel this away as e.g. sys.implementation._architecture for example. (The exact name can be bikeshedded to death, but re: PEP 421 must start with an underscore.) I now have a patch/branch that does this. lp:~barry/ubuntu/raring/python3.3/multiarch Yes, it's against Ubuntu Raring's Python 3.3 source branch, but that's just a copy of experimental's 3.3.0-5, and bzr+lp was the most convenient for this little bit of afternoon skunkworks. $ ./configure $ make $ ./python -c "import sys; print(sys.implementation._architecture)" x86_64-linux-gnu It should only be a little more difficult to backport this to Python 2.7 (I don't personally care about <=3.2 or <=2.7, and since this is all jessie-land stuff, y'all shouldn't either :), since there's no PEP 421 sys.implementation. Well, we can just hold our noses and stick the same thing in sys._architecture for 2.7. Notice the nice way this cleans up setup.py. Bonus! Feedback is most definitely welcome. If everyone thinks this is a good thing to pursue, I can clean up the patch, back port to 2.7, and Doko can sponsor it into experimental. Then I think we just hack our version of virtualenv to use sys._architecture (since it's currently a 2.x program) and we're done <wink>. Cheers, -Barry
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