My Lib

Makefile

CC = gcc
CFLAGS = -Wall -fPIC
LIBNAME = my_lib

all: $(LIBNAME).so

$(LIBNAME).so: my_lib.o
	$(CC) -shared -o $@ $^

my_lib.o: my_lib.c my_lib.h
	$(CC) $(CFLAGS) -c my_lib.c

clean:
	rm -f *.o *.so

my_lib.c

#include "my_lib.h"

int multiply(Numbers numbers)
{
    return numbers.a * numbers.b;
}

my_lib.h

#ifndef MYLIB_H
#define MYLIB_H

typedef struct
{
    int a;
    int b;
} Numbers;

int multiply(Numbers numbers);

#endif

my_lib.py

import ctypes

lib = ctypes.CDLL('./my_lib.so')

class Numbers(ctypes.Structure):
    _fields_ = [("a", ctypes.c_int), ("b", ctypes.c_int)]

numbers = Numbers(3, 4)

result = lib.multiply(numbers)
print(f"{numbers.a} * {numbers.b} = {result}")