[Python-Dev] Choosing a best practice solution for Python/extension modules (original) (raw)

Kevin Teague kevin at bud.ca
Sun Feb 22 00:35:59 CET 2009

So go ahead and tear this apart so that we can hopefully reach a consensus that makes sense so that at least testing can easily be done.

If I was developing an application and wanted to deal with two
different versions of the same library, I would simply make sure that
the version I wanted to use was first on sys.path. Perhaps something
such as:

lib/python-3.0/libdynload/ # extension module implementations lib/python-3.0/libpython/ # pure python implementations

Then in the test suite simply ensure that either the Python
implementation or the C implementation is first on sys.path. Both
directories would contain an _pickle.py module, and then pickle.py
could be changed from:

try: from _pickle import * except ImportError: Pickler, Unpickler = _Pickler, _Unpickler

To just:

from _pickle import Pickler, Unpickler

By default libdynload would be first on sys.path so that extension
modules would be imported first if available, otherwise it would
fallback to the pure Python versions. The test suite could then add/ remove libdynload from sys.path as needed.

Well, OK, so this is a pretty big change as to how standard lib files
are structured - so maybe there are quite a few reasons why this isn't
feasable ... but it does make things a lot simpler and gets rid of the
need for performing any magic with the loaded modules in the test suite.

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