Calling C from Python

Makefile

libsum.so: sum.c
	cc -shared -o libsum.so sum.c

sum.c

int our_function(int num_numbers, int *numbers) {
    int sum = 0;
    for (int i = 0; i < num_numbers; i++) {
        sum += numbers[i];
    }
    return sum;
}

sum.py

import ctypes

_sum = ctypes.CDLL('libsum.so')
_sum.our_function.argtypes = (ctypes.c_int, ctypes.POINTER(ctypes.c_int))

def our_function(numbers):
    num_numbers = len(numbers)
    array_type = ctypes.c_int * num_numbers
    result = _sum.our_function(ctypes.c_int(num_numbers), array_type(*numbers))
    return int(result)

if __name__ == '__main__':
	print(our_function([1, 2, 3, -10]))

Based on https://pgi-jcns.fz-juelich.de/portal/pages/using-c-from-python.html.