On Fri, Jul 24, 2009 at 10:39, Guido van Rossum <gu...@python.org> wrote:
> Still works, at least in some old 3.1 I had lying around: > > $ python3.1 > Python 3.1a0 (py3k:70152, Mar 3 2009, 16:55:42) > [GCC 4.0.1 (Apple Inc. build 5465)] on darwin > Type "help", "copyright", "credits" or "license" for more information. > >>> import sys > >>> sys.modules['string'] = None > >>> import string > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > ImportError: No module named string > >>> > $ python3.1 > Python 3.1a0 (py3k:70152, Mar 3 2009, 16:55:42) > [GCC 4.0.1 (Apple Inc. build 5465)] on darwin > Type "help", "copyright", "credits" or "license" for more information. > >>> import string > >>> > $ > > The experiment should be easily repeatable. :-) > =) Yes, the None raising ImportError semantics can be added easily and codified as official import semantics in 3.1. I was talking about the "None triggers another import as with relative imports" semantics and if there was some rather convoluted way to trigger that. I am guessing not as that would require a value of -1 for level which is no longer valid. I will fix importlib in both 3.2 and 3.1.1. And speaking of fixing, should I put the failing test in now and decorate it with unittest.expectedFailure until I get around to fixing it? -Brett > > --Guido > > On Thu, Jul 23, 2009 at 8:35 PM, Brett Cannon<br...@python.org> wrote: > > > > > > On Thu, Jul 23, 2009 at 20:18, Guido van Rossum <gu...@python.org> > wrote: > >> > >> So, I guess, we'll live with it for a while longer. Given that it > >> managed to evade our attention for so long, I think that's fine. > > > > Can someone double-check me that the semantics can even be triggered in > 3.1? > > I just tried and couldn't come up with anything. Heck, I quick search for > a > > Py_None comparison in 3.1's import.c turned up nothing useful (other than > > mark_miss() is the function used to set None in sys.modules). We might > have > > actually already removed it or made it so that the semantics can't be > > triggered. > > > >> > >> I agree that there's no reason for a None result from loaders to be > >> interpreted the same way, assuming that's not how it works ATM. > >> > >> And we can live with import and importlib differing on this in 3.1 > >> (though you could call it a bug in importlib and fix it for 3.1.1 -- > >> not sure if you were planning on that). > > > > I can if people can trigger the semantics somehow so I have a test to go > by. > > -Brett > > > >> > >> --Guido > >> > >> On Thu, Jul 23, 2009 at 7:50 PM, Brett Cannon<br...@python.org> wrote: > >> > > >> > > >> > On Thu, Jul 23, 2009 at 19:48, Benjamin Peterson <benja...@python.org > > > >> > wrote: > >> >> > >> >> 2009/7/23 Brett Cannon <br...@python.org>: > >> >> > > >> >> > > >> >> > On Thu, Jul 23, 2009 at 19:38, Benjamin Peterson > >> >> > <benja...@python.org> > >> >> > wrote: > >> >> >> > >> >> >> 2009/7/23 Brett Cannon <br...@python.org>: > >> >> >> > 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. > >> >> >> > >> >> >> I think it's still nice for the rare cases where you need to trick > a > >> >> >> module into thinking another one doesn't exist. > >> >> > > >> >> > But None does not strictly mean "I don't exist". None is supposed > to > >> >> > trigger > >> >> > an another import attempt for the module with a top-level name. > It's > >> >> > that > >> >> > extra import trigger that has no real use in 3.0 and just > complicates > >> >> > import > >> >> > semantics (IMO) needlessly. If you want a module to not exist then > >> >> > you > >> >> > either stick something else in (e.g. '42') or we remove the special > >> >> > semantics for None (which I thought we had). > >> >> > >> >> > >> >> I didn't realize None had other semantics attached to it. (Imagine > >> >> that dealing with import!) +1 for making it simply indicate an > >> >> ImportError. > >> > > >> > I'm +0 with having import raise ImportError if None is set in > >> > sys.modules as > >> > long as we don't suddenly expect loaders to trigger the same thing if > >> > they > >> > return None (actually, as of right now what loaders return count for > >> > nothing, but just want to be clear). > >> > -Brett > >> > >> > >> > >> -- > >> --Guido van Rossum (home page: http://www.python.org/~guido/) > > > > > > > > -- > --Guido van Rossum (home page: http://www.python.org/~guido/) >
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