[Cython] [cython-users] cimport numpy fails with Python 3 semantics

[Stefan Behnel]

Robert Bradshaw, 02.05.2012 09:15:
> On Sun, Apr 29, 2012 at 11:48 PM, Stefan Behnel wrote:
>> mark florisson, 28.04.2012 21:57:
>>> On 28 April 2012 19:50, Stefan Behnel wrote:
>>>> mark florisson, 28.04.2012 20:33:
>>>>> I think each module should have its own language level, so I think
>>>>> that's a bug. I think the rules should be:
>>>>>
>>>>>     - if passed as command line argument, use that for all cimported
>>>>> modules, unless they define their only language level through the
>>>>> directive
>>>>>     - if set as a directive, the language level will apply only to that module
>>>>
>>>> That's how it works. We don't run the tests with language level 3 in
>>>> Jenkins because the majority of the tests is not meant to be run with Py3
>>>> semantics. Maybe it's time to add a numpy_cy3 test.
>>>>
>>>> If there are more problems than just this (which was a bug in numpy.pxd),
>>>> we may consider setting language level 2 explicitly in numpy.pxd.
>>>
>>> Ah, great. Do we have any documentation for that?
>>
>> We do now. ;)
>>
>> However, I'm not sure cimported .pxd files should always inherit the
>> language_level setting. It's somewhat of a grey area because user provided
>> .pxd files would benefit from it since they likely all use the same
>> language level as the main module, whereas the Cython shipped (and
>> otherwise globally installed) .pxd files wouldn't gain anything and could
>> potentially break.
>>
>> I think we may want to keep the current behaviour and set the language
>> level explicitly in the few shipped .pxd files that are not language level
>> agnostic (i.e. those that actually contain code).
> 
> +1, I'm not worried about breaking the ones that ship with Cython, as
> we can manually specify the language level on those if necessary. This
> does have implications for automatically cimporting on import when a
> .pxd is found though, especially if one pulls in .pxd files from
> another project.

Right. Given that some people have started distributing .pxd files for some
C libraries on PyPI, we should advertise it in a visible part of the
documentation that authors of .pxd files have to take care to define a
language level if they depend on it.

Stefan