[Python-Dev] Proposing PEP 376 (original) (raw)

Tarek Ziadé ziade.tarek at gmail.com
Sun Apr 4 01:05:34 CEST 2010

On Fri, Apr 2, 2010 at 1:56 AM, Glyph Lefkowitz <glyph at twistedmatrix.com> wrote:

First: thank you distutils-sig, and especially Tarek, for spearheading this effort!

Thanks :)

I'm particularly excited about the "Distribution" object that this PEP specifies.  I've been waiting for a long time to be able to load an object describing a distribution, rather than running setup.py and hoping that it mutated the right state!

Notice that this Distribution class will work with installed distributions, where the info where built by running setup.py. As opposed to distritbutions that are not yet installed where these infos are still hidden in setup.py.

Although we are currently working in distutils2 to get rid of setup.py and have a pure static metadata file.

On Apr 1, 2010, at 5:51 PM, Tarek Ziadé wrote:

- to provide a basic uninstaller feature in the distutils2 project. Second: It seems to me that a major missing feature in the PEP is the ability to run some code during installation and uninstallation, especially since it is so easy to run ad-hoc code in setup.py with no way of un-doing what it did.

That was a feature request for distutils: install/removal hooks like what RPM or the msi installer offers. I think this could be done in distutils2 no matter what happens to the PEP. I am adding this in the bug tracker.

Third: The PEP is silent on what happens to files whose hash has changed from its install-time value.  I guess the implied plan would be to leave them in place.  However, this may have nasty side-effects; for example, if the files are test files, then they might be loaded during test discovery, and report exceptions since the code that they're testing has been removed.  My suggestion would be to have a specific "quarantine" area where the distutils uninstaller can put modified files that would have been removed as part of a specific distribution, so they aren't still present on PYTHONPATH.  I can also think of reasons why you might not want to do this, but either way, the consequence of changing an installed file should be made explicitly clear in the PEP: if they are to be left in place, it should emphasize that point.

The strategy about what should be done with modified files upon uninstallation is up to the implementation I guess. But the PEP should mention what Distutils2 basic uninstall function should do. The quarantine strategy sounds like a great idea. I propose to add this in the PEP in the implementation details section, and say in the specs that it's up to the implementation to decide.

Finally, one minor bit of bikeshedding, of which I promise to say nothing more if there is not unanimous agreement: I dislike the use of "get" in function names, since it adds more characters without really adding more information.  getfileusers is particularly bad, since it makes me think that it's going to return a list of processes with a file open, or a list of UIDs or something like that.  I suggest these names instead:  getdistributions() -> activedistributions()  getdistribution(name) -> activedistributionnamed(name)  getfileusers(path) -> distributionsusingpath(path) where "active" means "on the current sys.path and thereby accessible by 'import'".

"active" sounds superfluous too I think, since all distributions that are found are active. So it could be "distributions()". But I am not comfortable with this single word because it sounds to me like a sequence object rather than a function. But that might be just me..

This naming would also make the behavior of getfileusers a bit clearer; if the intention is to return only active, loadable distributions (you don't want to be able to use getfileusers to inspect other Python installations or virtualenvs) it could be called activedistributionsusingpath.

+1 on distributions_using_path()

Thanks again to the PEP's author and many contributors,

Thanks for the feedback !

-- Tarek Ziadé | http://ziade.org

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