[Distutils] Is there any harm in clearing sys.path_importer_cache from time to time?
jim at zope.com
Fri Jun 23 18:47:20 CEST 2006
On Jun 23, 2006, at 11:53 AM, Phillip J. Eby wrote:
> At 11:37 AM 6/23/2006 -0400, Jim Fulton wrote:
>> I have a script based on setuptools that invokes easy install to
>> check for
>> and download newer distributions. I allow users to specify
>> whether or
>> not they want unzipped downloads. As a result, easy_install will
>> replace a zip file with a directory or the other way around. This
>> leads to
>> problems in the invoking program because the sys.path_importer_cache
>> is stale. Does anyone know if it is safe to clear the cache from
>> time to
>> time? If so, I'd be inclined to clear it any time I invoke
> Hm. easy_install should be doing this itself... oh wait, it's
> clearing the *zip directory cache*, which fixes the problem of
> overwriting a zip with a zip. You're having a problem when
> overwriting a zip with a directory. Now I understand why sometimes
> I still get reports of behavior that resembles this problem, but
> then they aren't reproducible.
Actually, I happened to be having a problem overriding a directory
with a zip. This was in a test in which I demonstrate being able to
unzip and went back to not unzipping in a later example. After the
egg is reinstalled unzipped, the cache entry has None, left over from
finding the directory before.
This was in a doctest which invoked my buildout script as a
subprocess, which then invoked easy_install as a subprocess. When
the buildout script started, the egg in question was a directory. It
then ran easy_install, which replaced the directory with a zip file.
Then the buildout script tried to load the distribution for the
installed file, which failed.
I haven't been able to manually find the right combination to make
easy_install override a distribution manually, so I'm a bit puzzled.
If you wish me to pursue that I will.
> I'll fix easy_install to also clear the path importer cache for a
> path entry when it clears the zip directory cache for that entry.
OK. Note that that won't help me, because the cache I'm affected by
is in the parent
> (And to answer your general question, it's fine to clear the
> path_importer_cache, per PEP 302's advice to do so whenever you add
> new import hooks. It just slows down the next import search a bit.)
Cool, cause that solves my immediate problem. :)
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