I have just compiled part of my C library as an extension using Cython, as a \"proof of concept\". I managed to hack the code (const correctnes problems etc aside), to final
I had the same error and was solved by running the main .py script in "Execute in a dedicated console " mode. Available in Tools - Preferences - Run.
I've found that a frequent cause of this problem is, when using a distutils setup file to compile the code, that the .pyx base name does not match the extension name, e.g:
ext = Extension(name='different', sources=['cython_ext.pyx']) # Won't work
To avoid the problem the extension name should be exactly the same, in this case, cython_ext
.