[Cython] Cython inserting unqualified module name into sys.module on python 3?

[Sturla Molden]

Is this why I can only make scipy.spatial.cKDTree support pickle on Python
3? Since scipy.spatial.cKDTree comes from a relative import of
.ckdtree.cKDTree into scipy.spatial, it somehow works on Python 3 but fails
on Python 2.

Sturla


Nathaniel Smith <njs at vorpus.org> wrote:
> On Mar 14, 2015 2:03 PM, "Robert Bradshaw"
> <robertwb at gmail.com> wrote:
>> 
>> That is strange, looks like it was an attempt to support relative imports?
>> 
>> https://github.com/cython/cython/blob/384cc660f5c7958524b8839ba24099fdbc6eaffd/Cython/Compiler/ModuleNode.py#L2271
> 
> Ah, I see.
> 
> I don't see how this could affect relative imports, because if foo.bar
> does 'import .baz', this doesn't actually trigger any access to
> sys.modules["foo.bar"]. (Exception: if you have foo/__init__.pyx. Is
> that actually supported?) The critical thing for relative imports is
> having correct __name__ and/or __package__ module-level global
> variables, and AFAICT cython is not currently doing anything to set
> these up. But it probably should, because relative imports are a
> thing.
> 
> OTOH, putting the module into sys.modules *is* crucial to handle
> recursive imports, i.e. where foo.pyx's module init function imports
> bar.py, and bar.py imports foo. For regular python modules or for
> python 2 extension modules, this works because even while foo is still
> initializing, you can already get its (incomplete) module object from
> sys.modules; for python 3 extension modules this won't work unless we
> do it by hand. So the code that Cython is generating seems to be
> correct and necessary, it just has the wrong idea about what the
> fully-qualified module name is, and this breaks things.
> 
> So I'm convinced that Cython has to know the fully-qualified module
> name for correct operation, and if it's wrong then weird real bugs
> will happen. Next question: how am I supposed to make this work? Maybe
> I'm just missing it, but I can't find anything in the docs about how I
> should tell cython that mtrand.pyx is really numpy.random.mtrand...?
> 
> -n
> 
>> On Sat, Mar 14, 2015 at 1:17 AM, Nathaniel Smith
>> <njs at vorpus.org> wrote:
>>> Hi all,
>>> 
>>> Can anyone shed any light on this?
>>> 
>>> https://github.com/numpy/numpy/issues/5680
>>> 
>>> -n
>>> 
>>> --
>>> Nathaniel J. Smith -- http://vorpus.org
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