language binding

foo.cpp

#include "foo.h"

void 
Foo::hello(){
  std::cout << "Hello world" << std::endl;
}

int
Foo::add(int a, int b){
  return a + b;
}

int
Foo::sub(int a, int b){
  return a - b;
}

int
Foo::mul(int a, int b){
  return a * b;
}

float
Foo::div(int a, int b){
  return (b)? (float)a/b : 0; 
}

foo.h

#include <iostream>

class Foo{
  public:
    void hello();
    int add(int a, int b);
    int sub(int a, int b);
    int mul(int a, int b);
    float div(int a, int b);
};

extern "C" {
  Foo* Foo_new(){ return new Foo(); }
  void Foo_hello(Foo* foo){ foo->hello(); }
  int Foo_add(Foo* foo, int a, int b){ return foo->add(a, b); }
  int Foo_sub(Foo* foo, int a, int b){ return foo->sub(a, b); }
  int Foo_mul(Foo* foo, int a, int b){ return foo->mul(a, b); }
  float Foo_div(Foo* foo, int a, int b){ return foo->div(a,b); }
}

foo.py

from ctypes import cdll, c_void_p, c_float, c_int
lib = cdll.LoadLibrary('./libfoo.so')

# You need to specify the parameter and return types needed 
# by the functions in your library that you intend to call.
# Arguments types)  
#   cdll.LoadLibrary('YOUR_PATH').FUNC_NAME.argtypes = [arg_type1, arg_type2, ...]
# Retuen type)
#   cdll.LoadLibrary('YOUR_PATH').FUNC_NAME.restype = [return_type]
# List of type : https://docs.python.org/2/library/ctypes.html#fundamental-data-types 

class Foo(object):
    def __init__(self):
        # Set the arguments types and return type
        # new)
        lib.Foo_new.restypes = c_void_p
        # add)
        lib.Foo_add.argtypes = [c_void_p, c_int, c_int]
        lib.Foo_add.restype = c_int
        # sub)
        lib.Foo_add.argtypes = [c_void_p, c_int, c_int]
        lib.Foo_sub.restype = c_int
        # mul)
        lib.Foo_add.argtypes = [c_void_p, c_int, c_int]
        lib.Foo_mul.restype = c_int
        # div)
        lib.Foo_add.argtypes = [c_void_p, c_int, c_int]
        lib.Foo_div.restype = c_float
        # Create a new object of Foo class
        self.obj = lib.Foo_new()
   
    def printOp(self, a, b, opStr):
        print str(a) + ' ' + opStr + ' ' + str(b) + ' =',

    def hello(self):
        lib.Foo_hello(self.obj)
    
    def add(self, a, b):
        self.printOp(a, b, '+')
        return lib.Foo_add(self.obj, a , b)
    
    def sub(self, a, b):
        self.printOp(a, b, '-')
        return lib.Foo_sub(self.obj, a , b)
    
    def mul(self, a, b):
        self.printOp(a, b, '*')
        return lib.Foo_mul(self.obj, a , b)
    
    def div(self, a, b):
        self.printOp(a, b, '/')
        return lib.Foo_div(self.obj, a , b)

f = Foo()
f.hello()
print f.add(1,2)
print f.sub(3,4)
print f.mul(5,6)
print f.div(7,8)

makefile

# Compiler to use
CC = g++
# Source file name
SRC = foo.cpp
# Object file name -> foo.o
OBJ = $(SRC:.cpp=.o)
# Shared library name -> libfoo.so
SHRLIB = $(addprefix lib, $(OBJ:.o=.so))  

# Make Commands
all: $(OBJ) $(SHRLIB)

$(OBJ):
	$(CC) -c -fPIC $(SRC) -o $(OBJ)

$(SHRLIB):
	$(CC) -shared -Wl,-soname,$(SHRLIB) -o $(SHRLIB)  $(OBJ)

clean:
	rm foo.o libfoo.so