[Python-Dev] Re: .DLL vs .PYD search order

[James C. Ahlstrom]

"M.-A. Lemburg" wrote:

> An example:
> 
> A path importer knows how to scan directories and how to use
> a path to tell the correct order. It can maybe also import
> .py/.pyc/.pyo files. Now what happens if it finds a shared
> lib as module... the usual imputil way would be to delegate
> the request to some other importer which can handle shared
> libs... but wait: how does the shared lib importer know
> where to look ? It will have to rescan the directories,
> etc...

The above refers to an earlier but still very recent version
of imputil.  On that basis is is perfectly accurate.  Here is
another example from my own experience almost identical to
the above:

One possible archive file format holds its list of archived
*.pyc file names as keys in a dictionary.  This is simple and
efficient, but fails to correctly address the problem of shared
libs (aka DLL's in Windows) with names identical to names of
*.pyc files in the archive.  For example, suppose foo.pyc is in the
archive, and foo.dll is in a directory.  Suppose sys.path is to be
used to decide whether to load foo.pyc or foo.dll.  Then an
"archive importer" will fail to do this.  Specifically you can't
see if foo.pyc is in the archive and then check sys.path, nor can
you do the reverse.  You must call the "archive importer" repeatedly
for each element of sys.path and search the directory at the same time.

JimA