[Python-Dev] requirements for moving import over to importlib? (original) (raw)

Terry Reedy tjreedy at udel.edu
Fri Feb 10 04:14:16 CET 2012

On 2/9/2012 7:19 PM, PJ Eby wrote:

Right. It was the part of the post that mentioned that all they sped up was knowing which directory the files were in, not the actual loading of bytecode. The thought then occurred to me that this could perhaps be applied to normal importing, as a zipimport-style speedup. (The zipimport module caches each zipfile directory it finds on sys.path, so failed import lookups are extremely fast.)

It occurs to me, too, that applying the caching trick to only the stdlib directories would still be a win as soon as you have between four and eight site-packages (or user specific site-packages) imports in an application, so it might be worth applying unconditionally to system-defined stdlib (non-site) directories.

It might be worthwhile to store a single file in in the directory that contains /Lib with the info inport needs to get files in /Lib and its subdirs, and check that it is not outdated relative to /Lib. Since in Python 3, .pyc files go in pycache, if /Lib included an empyty pycache on installation, /Lib would never be touched on most installations. Ditto for the non-pycache subdirs.

-- Terry Jan Reedy

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