I just installed numpy for both python2 and 3 from an up-to-date checkout of the 1.5.x branch. I am attempting to cythonize the following code with cython-0.13: --- cimport numpy as np import numpy as np def test(): cdef np.ndarray[np.float64_t, ndim=1] ret ret_arr = np.zeros((20,), dtype=np.float64) ret = ret_arr --- I have this setup.py file: --- from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext import numpy setup( cmdclass = {'build_ext': build_ext}, ext_modules = [ Extension( "test_open", ["test_open.pyx"], include_dirs=[numpy.get_include()] ) ] ) --- When I run "python setup.py build_ext --inplace", everything is fine. When I run "python3 setup.py build_ext --inplace", I get an error: running build_ext cythoning test_open.pyx to test_open.c Error converting Pyrex file to C: ------------------------------------------------------------ ... # For use in situations where ndarray can't replace PyArrayObject*, # like PyArrayObject**. pass ctypedef class numpy.ndarray [object PyArrayObject]: cdef __cythonbufferdefaults__ = {"mode": "strided"} ^ ------------------------------------------------------------ /home/darren/.local/lib/python3.1/site-packages/Cython/Includes/numpy.pxd:173:49: "mode" is not a buffer option Error converting Pyrex file to C: ------------------------------------------------------------ ... cimport numpy as np import numpy as np def test(): cdef np.ndarray[np.float64_t, ndim=1] ret ^ ------------------------------------------------------------ /home/darren/temp/test/test_open.pyx:6:8: 'ndarray' is not a type identifier building 'test_open' extension gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/home/darren/.local/lib/python3.1/site-packages/numpy/core/include -I/usr/include/python3.1 -c test_open.c -o build/temp.linux-x86_64-3.1/test_open.o test_open.c:1: error: #error Do not use this file, it is the result of a failed Cython compilation. error: command 'gcc' failed with exit status 1 Is this a bug, or is there a problem with my example? Thanks, Darren