Cython Numpy warning about NPY_NO_DEPRECATED_API when using MemoryView

Question

I am converting a Cython memoryview to a numpy array (to be able to use it in pure Python code):

from libc.stdlib cimport realloc
cimport numpy as np

DTYPE = np.float64
ctypedef np.float64_t DTYPE_t

cpdef np.ndarray[DTYPE_t] compute(DTYPE_t[:,::1] data):
    cdef unsigned int Nchannels = data.shape[0]
    cdef unsigned int Ndata = data.shape[1]
    cdef DTYPE_t* output = NULL
    cdef DTYPE_t[::1] mv

    output = <DTYPE_t*>realloc(output, Ndata*sizeof(output))
    if not output:
        raise MemoryError()
    mv = <DTYPE_t[:Ndata]>output
    mv[10:Ndata-10] = 0.0
    # various calculations...
    return np.asarray(mv, dtype=DTYPE, order='C')

It compiles, but the compiler gives the following warning:

/Users/vlad/anaconda/lib/python2.7/site-packages/numpy/core/include
/nump/npy_1_7_deprecated_api.h:15:2: warning:
"Using deprecated NumPy API, disable it by #defining NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION" [-W#warnings]

I added the suggested directive in setup.py:

from distutils.core import setup, Extension
from Cython.Build import cythonize
import numpy

filename = 'agents3.pyx'

agents_module = Extension(
    'Agents',
    sources = [filename],
    define_macros = [('NPY_NO_DEPRECATED_API', 'NPY_1_7_API_VERSION')],
    include_dirs = [numpy.get_include()],
)

setup (name = 'Agents',
    ext_modules = cythonize(agents_module)
)

Now it wouldn't compile, it says:

Vlads-MacBook-Pro:program vlad$ python setup.py build_ext --inplace
Compiling agents3.pyx because it changed.
Cythonizing agents3.pyx
running build_ext
building 'Agents' extension
gcc -fno-strict-aliasing -I/Users/vlad/anaconda/include -arch x86_64 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -DNPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION -I/Users/vlad/anaconda/lib/python2.7/site-packages/numpy/core/include -I/Users/vlad/anaconda/include/python2.7 -c agents3.c -o build/temp.macosx-10.5-x86_64-2.7/agents3.o
agents3.c:2273:52: error: use of undeclared identifier 'NPY_C_CONTIGUOUS'
    __pyx_t_2 = ((!(PyArray_CHKFLAGS(__pyx_v_self, NPY_C_CONTIGUOUS) != 0)) != 0);
                                                   ^
agents3.c:2311:52: error: use of undeclared identifier 'NPY_F_CONTIGUOUS'
    __pyx_t_1 = ((!(PyArray_CHKFLAGS(__pyx_v_self, NPY_F_CONTIGUOUS) != 0)) != 0);
                                                   ^
agents3.c:2474:42: error: no member named 'descr' in 'struct tagPyArrayObject'
  __pyx_t_4 = ((PyObject *)__pyx_v_self->descr);
                           ~~~~~~~~~~~~  ^
agents3.c:4026:27: error: no member named 'base' in 'struct tagPyArrayObject'
  Py_XDECREF(__pyx_v_arr->base);
             ~~~~~~~~~~~  ^
/Users/vlad/anaconda/include/python2.7/object.h:823:34: note: expanded from macro 'Py_XDECREF'
#define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)
                                 ^
agents3.c:4026:27: error: no member named 'base' in 'struct tagPyArrayObject'
  Py_XDECREF(__pyx_v_arr->base);
             ~~~~~~~~~~~  ^
/Users/vlad/anaconda/include/python2.7/object.h:823:64: note: expanded from macro 'Py_XDECREF'
#define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)
                                                               ^
/Users/vlad/anaconda/include/python2.7/object.h:772:24: note: expanded from macro 'Py_DECREF'
        --((PyObject*)(op))->ob_refcnt != 0)            \
                       ^
agents3.c:4026:27: error: no member named 'base' in 'struct tagPyArrayObject'
  Py_XDECREF(__pyx_v_arr->base);
             ~~~~~~~~~~~  ^
/Users/vlad/anaconda/include/python2.7/object.h:823:64: note: expanded from macro 'Py_XDECREF'
#define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)
                                                               ^
/Users/vlad/anaconda/include/python2.7/object.h:775:34: note: expanded from macro 'Py_DECREF'
        _Py_Dealloc((PyObject *)(op));                  \
                                 ^
/Users/vlad/anaconda/include/python2.7/object.h:762:15: note: expanded from macro '_Py_Dealloc'
    (*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
              ^
/Users/vlad/anaconda/include/python2.7/object.h:115:47: note: expanded from macro 'Py_TYPE'
#define Py_TYPE(ob)             (((PyObject*)(ob))->ob_type)
                                              ^
agents3.c:4026:27: error: no member named 'base' in 'struct tagPyArrayObject'
  Py_XDECREF(__pyx_v_arr->base);
             ~~~~~~~~~~~  ^
/Users/vlad/anaconda/include/python2.7/object.h:823:64: note: expanded from macro 'Py_XDECREF'
#define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)
                                                               ^
/Users/vlad/anaconda/include/python2.7/object.h:775:34: note: expanded from macro 'Py_DECREF'
        _Py_Dealloc((PyObject *)(op));                  \
                                 ^
/Users/vlad/anaconda/include/python2.7/object.h:762:45: note: expanded from macro '_Py_Dealloc'
    (*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
                                            ^
agents3.c:4035:16: error: no member named 'base' in 'struct tagPyArrayObject'
  __pyx_v_arr->base = __pyx_v_baseptr;
  ~~~~~~~~~~~  ^
agents3.c:4070:30: error: no member named 'base' in 'struct tagPyArrayObject'
  __pyx_t_1 = ((__pyx_v_arr->base == NULL) != 0);
                ~~~~~~~~~~~  ^
agents3.c:4093:44: error: no member named 'base' in 'struct tagPyArrayObject'
    __Pyx_INCREF(((PyObject *)__pyx_v_arr->base));
                              ~~~~~~~~~~~  ^
agents3.c:1065:37: note: expanded from macro '__Pyx_INCREF'
  #define __Pyx_INCREF(r) Py_INCREF(r)
                                    ^
/Users/vlad/anaconda/include/python2.7/object.h:767:18: note: expanded from macro 'Py_INCREF'
    ((PyObject*)(op))->ob_refcnt++)
                 ^
agents3.c:4094:41: error: no member named 'base' in 'struct tagPyArrayObject'
    __pyx_r = ((PyObject *)__pyx_v_arr->base);
                           ~~~~~~~~~~~  ^
11 errors generated.
error: command 'gcc' failed with exit status 1
Vlads-MacBook-Pro:program vlad$

What should I do? Is it OK to leave the deprecated API call as it is? It tries to acces the base field -- but I am not doing it, it's Cython's fault. I simply converted a memoryview to a numpy array. Is there another, cleaner/safer way of doing it?

FWIW, I get the same warnings. It hasn't broken anything yet, so I'm ignoring them for now. — perimosocordiae, Sep 11 '14 at 17:04

score 49 · Accepted Answer · answered Aug 13 '15 at 12:42

49

Just for a further reference, cython online docs says this is because Cython is using a deprecated Numpy API, and for the time being, it's just a warning that we can ignore.

answered Aug 13 '15 at 12:42

Jianxun Li

22,380
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Thank you! I chose your answer because it's not only your guess, but you brought evidence. :) – Amenhotep Aug 14 '15 at 14:01
1

OK, but the warning is written to stdout, so it's annoying to filter. Can one configure cython to not report warnings? – Arthur Feb 26 '16 at 17:29
1

@Arthur If you're using cython magic in ipython then you can use `%%cython --compile-args=-w` to disable warnings. – towr Aug 08 '16 at 07:47
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The online doc section has moved to http://docs.cython.org/en/latest/src/userguide/source_files_and_compilation.html#configuring-the-c-build – Demi-Lune Jun 18 '19 at 07:39
To summarize [above doc](http://docs.cython.org/en/latest/src/userguide/source_files_and_compilation.html#configuring-the-c-build): as of 2021, version cython 3.0 (still pre-release at the time of writing) addresses that issue, with earlier cython version keep ignoring the warning. – Nikolay Nov 05 '21 at 00:04

score 0 · Answer 2 · answered Mar 12 '15 at 10:07

I also get the same warnings, and I'd say it's normal.

With the numpy C API you need to put a line in front of the C script if you don't like this warning, but all it does is tell the compiler to ignore the "deprecated" message - it seems to work the same either way.

I'm guessing the Cython compiler doesn't put this line of code when it generates the C code, and I don't think that's important.

score 0 · Answer 3 · edited Mar 23 '19 at 07:50

0

Assuming one wishes to hide the deprecation warning, the following compiler flag can be implemented with clang: extra_compile_args=['-Wno-#warnings'].

For gcc, extra_compile_args=['-Wno-cpp'] achieves the same.

Of course this also hides other preprocessor directive warnings.

edited Mar 23 '19 at 07:50

Richard

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answered Oct 05 '16 at 15:24

Thomas Riley

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That's bad habit to deprecate warnings – Maksym Ganenko Jun 20 '18 at 09:57

Cython Numpy warning about NPY_NO_DEPRECATED_API when using MemoryView

3 Answers3

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