Pass numpy array as C pointers in Cython, ref: https://github.com/cython/cython/wiki/tutorials-NumpyPointerToC

print_np_as_c.pyx

import cython
cimport cython
import numpy as np
cimport numpy as np

cdef extern from "utils.h":
  void print_array(double *, int)
  
def print_np_as_c(np.ndarray[double, ndim=2, mode="c"] arr not None):
  cdef int n
  n = arr.shape[0] * arr.shape[1]
  print_array(&arr[0, 0], n)

setup.py

from distutils.core import setup
from distutils.extension import Extension
from Cython.Build import cythonize

import numpy

setup(
    ext_modules = cythonize( [Extension('print_np_as_c', 
    									sources=['print_np_as_c.pyx', 'utils.c'],
    									include_dirs=[numpy.get_include()],
    									define_macros=[("NPY_NO_DEPRECATED_API",None)]),
                            ] )
     )

# python setup.py build_ext --inplace

test.py

import numpy as np
import print_np_as_c

arr = np.random.rand(2, 3)
print_np_as_c.print_np_as_c(arr)

utils.c

#include <stdio.h>

void print_array(double * arr, int n) {
  for(int i = 0; i < n; i++)
    print("%f\n", arr[i]);
}

utils.h

void print_array(double * arr, int n);