On Thu, Jul 23, 2009 at 13:05, Guido van Rossum <gu...@python.org> wrote:
> On Thu, Jul 23, 2009 at 12:09 PM, Fred Drake<fdr...@acm.org> wrote: > > On Jul 23, 2009, at 2:59 PM, Georg Brandl wrote: > >> > >> is the presence of None values in sys.modules considered an > implementation > >> detail? If not, it should be documented what the None values mean to > the > >> interpreter. > > > > As I recall, they're an optimization. But since sys.modules is itself > > documented, and many applications actually use it, I think it's worth > > explaining that the None values can reasonably be expected, and what they > > indicate. > > They should certainly be documented -- without them imports from > inside package would be super expensive (at least for Python versions > where implicit relative import exists). I'm somewhat surprised this > isn't documented, I don't think I've tried to keep this usage hidden. > I've also sometimes abused this to force some module to believe that a > certain other module doesn't exist. > It has not been hidden, but the only place I ever came across it was in the original essay about packages. > > OTOH in Py3k I'm not sure that we even *need* them any more, since > there is no more implicit relative import... They would only speed up > the raising of ImportError, not the finding of a similar-named module > elsewhere in the hierarchy. None in Python 3.1 is really useless in terms of its semantics in relative imports; importlib doesn't support it and still passes as __import__ (at least last time I ran the test suite that way). I thought we had agreed a while back that supporting None was not warranted in Python 3.0? Otherwise I will do whatever work is necessary for this to happen. -Brett
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