Embed python / numpy in C++

#define NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION

#include <stdio.h>
#include <iostream>
#include <stdlib.h>

#include <Python.h>
#include "numpy/arrayobject.h"

int main(int argc, char* argv[])
{
    setenv("PYTHONPATH", ".", 0);

    Py_Initialize();
    import_array();

    // Build the 2D array in C++
    const int SIZE = 3;
    npy_intp dims[2] {SIZE, SIZE};
    const int ND = 2;
    long double(*c_arr)[SIZE] { new long double[SIZE][SIZE] };

    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++) {
            c_arr[i][j] = i + j;
        }
    }

    // Convert it to a NumPy array.
    PyObject* pArray = PyArray_SimpleNewFromData(ND, dims, NPY_LONGDOUBLE,
                       reinterpret_cast<void*>(c_arr));

    // import mymodule
    const char* module_name = "mymodule";
    PyObject* pName = PyUnicode_FromString(module_name);
    PyObject* pModule = PyImport_Import(pName);
    Py_DECREF(pName);

    // import function
    const char* func_name = "array_tutorial";
    PyObject* pFunc = PyObject_GetAttrString(pModule, func_name);
    PyObject* pReturn = PyObject_CallFunctionObjArgs(pFunc, pArray, NULL);
    PyArrayObject* np_ret = reinterpret_cast<PyArrayObject*>(pReturn);

    // Convert back to C++ array and print.
    int len = PyArray_SHAPE(np_ret)[0];
    long double* c_out;
    c_out = reinterpret_cast<long double*>(PyArray_DATA(np_ret));
    std::cout << "Printing output array - C++" << std::endl;

    for (int i = 0; i < len; i++) {
        std::cout << c_out[i] << ' ';
    }

    std::cout << std::endl << std::endl;


    // import function without arguments
    const char* func_name2 = "myfunction";
    PyObject* pFunc2 = PyObject_GetAttrString(pModule, func_name2);
    PyObject* pReturn2 = PyObject_CallFunctionObjArgs(pFunc2, NULL);
    PyArrayObject* np_ret2 = reinterpret_cast<PyArrayObject*>(pReturn2);

    // convert back to C++ array and print
    int len2 = PyArray_SHAPE(np_ret2)[0];
    long double* c_out2;
    c_out2 = reinterpret_cast<long double*>(PyArray_DATA(np_ret2));
    std::cout << "Printing output array 2 - C++" << std::endl;

    for (int i = 0; i < len2; i++) {
        std::cout << c_out2[i] << ' ';
    }

    std::cout << std::endl << std::endl;

    Py_Finalize();
    return 0;
}

import numpy

def array_tutorial(a):
    print("array_tutorial - python")
    print(a)
    print(numpy.dtype(a[0,0]))
    print("")
    firstRow = a[0,:]
    #beta = numpy.array([[10,20,30],[10,20,30],[10,20,30]],dtype=numpy.float128)
    #firstRow = beta[0,:]
    return firstRow

def myfunction():
    beta = numpy.array([[1,2,3],[1,2,3],[1,2,3]],dtype=numpy.float128)
    print("myfunction - python")
    print(beta)
    print("")
    firstRow = beta[0,:]
    return firstRow

• Makefile

CC = g++
LDFLAGS = -lm -lpthread -ldl -lutil -lpython3.6m 
CFLAGS = -Wall -pedantic -ggdb3 -O0
INCLUDE = -I/home/shihyu/anaconda3/include/python3.6m
LIB = -L/home/shihyu/anaconda3/lib

SOURCEDIR = ./
BUILDDIR = build
SRCS = $(wildcard $(SOURCEDIR)/*.cpp)
OBJS = $(addprefix $(BUILDDIR)/,$(notdir $(SRCS:.cpp=.o)))

all : dir process 

dir :
    mkdir -p $(BUILDDIR)

process : $(OBJS)
    $(CC) -o $@ $(CFLAGS) $(OBJS) $(LIB) $(LDFLAGS)

$(BUILDDIR)/%.o : $(SOURCEDIR)/%.cpp
    $(CC) $(INCLUDE) $(CFLAGS) -c $< -o $@

clean:
    rm -rf process hello.pyc $(BUILDDIR)

 export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/shihyu/anaconda3/lib

 ./process

 array_tutorial - python
[[0. 1. 2.]
 [1. 2. 3.]
 [2. 3. 4.]]
float128

Printing output array - C++
0 1 2 

myfunction - python
[[1. 2. 3.]
 [1. 2. 3.]
 [1. 2. 3.]]

Printing output array 2 - C++
1 2 3