I am trying to use explicit relative imports in cython. From the release notes it seems like relative imports should work after cython 0.23, and I'm using 0.23.4 with python 3.5. But I get this strange error that I cannot find many references to. The error is only from the cimport:
driver.pyx:4:0: relative cimport beyond main package is not allowed
The directory structure is:
myProject/
setup.py
__init__.py
test/
driver.pyx
other.pyx
other.pxd
It seems like I'm probably messing up in setup.py so I included all the files below.
setup.py
from setuptools import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext
ext_modules = [
Extension('other', ['test/other.pyx'],),
Extension('driver', ['test/driver.pyx'],),
]
setup(
name='Test',
ext_modules=ext_modules,
include_dirs=["test/"],
cmdclass={'build_ext': build_ext},
)
driver.pyx
#!/usr/bin/env python
from . import other
from . cimport other
other.pyx
#!/usr/bin/env python
HI = "Hello"
cdef class Other:
def __init__(self):
self.name = "Test"
cdef get_name(self):
return self.name
other.pxd
cdef class Other:
cdef get_name(self)
I've tried moving __init__.py into test/. I've tried running setup.py in the test directory (adjusting the include_dirs appropriately). They both give the same error.
If I do cimport other and remove the . it works but this is a toy example and I need relative imports so other folders can import properly. This is the only example I can find for this error and I'm pretty confident my issue is different.
The only other example I could find of this error was in hal.pyx of the machinekit project. I was pretty confident that this was a different error but today I realized that after that error was solved machinekit was working which means explicit relative imports must work. Their setup.py file refers to linuxcnc which isn't in the directory tree but I guess is created at some point during compile time. The important thing is that the include_dirs includes the parent directory instead of the child directory.
Translated to my project structure it would mean I put myProject in include_dirs instead of test/. After read this guide for the second time I finally started to understand a little of how python thinks of packages. The problem was that the include_dirs was the child directory. It seems like this effectively made cython view it as a single flat directory in which case no relative imports would be allowed? An error like this might have made it more clear:
ValueError: Attempted relative import in non-package
I still don't have a sufficiently deep understanding to know exactly what was going on but luckily the solution was relatively simple. I just changed the include_dirs to make cython recognize the nested file structure:
from setuptools import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext
ext_modules = [
Extension('other', ['test/other.pyx'],),
Extension('driver', ['test/driver.pyx'],),
]
setup(
name='Test',
ext_modules=ext_modules,
include_dirs=["."],
cmdclass={'build_ext': build_ext},
)
It all works now!