ctypes examples

mylib.c

// gcc -std=c99 -O3 -fPIC -shared -Wl,-soname,mylib -o mylib.so mylib.c

#include <stdio.h>
#include <complex.h>

int build_hamiltonian(int i, double d, complex double *m)
{
    m[0]=2.*I;
    return 0;
}

numpy_array.py

import numpy as np
from numpy.ctypeslib import ndpointer
from ctypes import *

class PointerWrapper(object):
    """Just like ndpointer, but accept None!"""
    def __init__(self,pointer):
        self.pointer=pointer
    def from_param(self,param):
        if param!=None:
            return self.pointer.from_param(param)
        else:
            return POINTER(c_double).from_param(None)

mylib=CDLL('/tmp/mylib.so')
mylib.myfunc.argtypes=[c_int,c_double,PointerWrapper(ndpointer(dtype=np.complex128,ndim=2,flags='C'))]
mylib.myfunc.restype=c_int

m=np.zeros((2,2),dtype=np.complex128)
mylib.myfunc(1,0.5,m)
print m