ToDay

I wrote the other day

Call the code generated by Cython from C / C ++ (Windows version)

Let's try the Mac version of. It is assumed that Python is using one of the environments in pyenv.

Prepare Cython code

Let's define a vertex structure and create a function that returns a vertex structure with doubled coordinates.

`cytest.pyx`


cdef public struct Point:
    double x
    double y

cdef public Point DoubleCoord(Point p):
    cdef Point q
    q.x=2*p.x
    q.y=2*p.y
    return q

Also prepare setup.py.

`setup.py`


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

setup(ext_modules=cythonize("cytest.pyx"))

Code generation

$ python setup.py build_ext --inplace

By doing this, cytest.h`` cytest.c should be generated.

Call code creation

Let's write the code as below.

`call.c`


#include <stdio.h>
#include <Python.h>
#include "cytest.h"

int main(int argc, char const *argv[])
{
    Py_Initialize();
    struct Point p;
    p.x=3.0;
    p.y=4.0;
    struct Point q = DoubleCoord(p);
    printf("Hello\n");
    printf("q.x=%f,q.y=%f\n",q.x,q.y);
    Py_Finalize();
    /* code */
    return 0;
}

One thing to note here is that you have to include Python.h before including cytest.h.

error: unknown type name 'PyMODINIT_FUNC'

I get angry.

Before let's build

Here, I will try it in the case of 3.5.4 in the pyenv environment.

$ pyenv global
3.5.4

First you have to find out where the Python.h is. As conclusion

$HOME/.pyenv/versions/3.5.4/include/python3.5m

Then, if you look at it in Finder, you will see that the header files are lined up.

Rinka looks for the library, so I have to tell her the location. There is lib in the same hierarchy as ʻinclude`, so let's take a look here.

You found it.

Let's build

How to use the compiler (gcc command)

Let's write it with reference to.

gcc -Wall -I $HOME/.pyenv/versions/3.5.4/include/python3.5m -L $HOME/.pyenv/versions/3.5.4/lib -lpython3.5m call.c cytest.c

Then the executable file ʻa.out` will be created.

$ ./a.out 
Hello
q.x=6.000000,q.y=8.000000

It was confirmed that the vertex coordinates were doubled. Now you can call Python from C / C ++ and vice versa via Cython, so you can work from any direction.

[PYTHON] Call the code generated by Cython from C / C ++ (Mac version)