On Jun 9, 2009, at 11:03 AM, Ondrej Certik wrote:
> Hi,
>
> I have the following problem -- I have a package hermes2d, with the
> structure:
>
> hermes2d/__init__.py
> hermes2d/_hermes2d.pyx + .pxd
> hermes2d/_forms.pyx
>
> and sometimes (depending on what the users tells cmake) I want to
> build the .so libraries out of the tree and put their paths to
> PYTHONPATH. Things just work as long as remove the file
> hermes2d/__init__.py during the cython compilation. The reason is that
> if I do:
>
> cd hermes2d
> cython _forms.pyx
>
> it produces _forms.c with lines like:
>
> __pyx_ptype_8hermes2d_9_hermes2d_LinSystem =
> __Pyx_ImportType("hermes2d._hermes2d", "LinSystem", sizeof(struct
> __pyx_obj_8hermes2d_9_hermes2d_LinSystem)); if
> (unlikely(!__pyx_ptype_8hermes2d_9_hermes2d_LinSystem))
> {__pyx_filename = __pyx_f[1]; __pyx_lineno = 292; __pyx_clineno =
> __LINE__; goto __pyx_L1_error;}
>
> Notice the import "hermes2d._hermes2d", which fails if _hermes2d.so is
> out of the tree (e..g somewhere else on the filesystem, even if it's
> in the search path!). If, however I remove the __init__.py, then
> cython generates:
>
> __pyx_ptype_9_hermes2d_LinSystem = __Pyx_ImportType("_hermes2d",
> "LinSystem", sizeof(struct __pyx_obj_9_hermes2d_LinSystem)); if
> (unlikely(!__pyx_ptype_9_hermes2d_LinSystem)) {__pyx_filename =
> __pyx_f[1]; __pyx_lineno = 292; __pyx_clineno = __LINE__; goto
> __pyx_L1_error;}
>
> and everything just works, no matter where the file _hermes2d.so
> actually is.
>
> Now my question is -- if I want those .so libraries not to be in the
> tree, am I doing things the right way? E.g. I just have a line:
>
> from _forms import *
>
> in the hermes2d/forms.py
>
> and then people just do "from hermes2d import forms" and things work,
> no matter where the .so files are. But I need some way to force cython
> to just pretend there is no __init__.py in there. Why is cython doing
> this check at all? Does it have any advantages?
One advantage I see is that you may have two modules named _hermes2d
in different packages that it might have to distinguish. (OK, rare
with that name, but it could happen with more common names). Also,
this way the module path is fully qualified as one would expect.
- Robert
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