Connecting C++ to Python using Boost.Python...

Many modern C++ applications provide a Python interface because it combines performance (C++) with ease of use (Python). Here’s why this trend has become so popular: ✔ It allows rapid prototyping. ✔ It combines speed (C++) with flexibility (Python). ✔ Python is popular in AI, ML, and scientific computing. ✔ Users can extend software via Python scripting. Boost.Python is a powerful library that enables seamless integration between C++ and Python. It allows C++ functions and classes to be exposed to Python, enabling direct interaction between the two languages. As I was playing around with Boost.Python, I made my existing Factory Pattern project written in C++ to expose itself to the python using Boost.Python library. The most important part is the following lines of code. This is kind of self explanatory - how we expose the C++ classes and methods to Python code. // Expose Singleton Factory to Python BOOST_PYTHON_MODULE(FactoryPattern) { using namespace boost::python; class_("Food", no_init) .def("getName", pure_virtual(&Food::getName)); class_("Biscuit") .def("getName", &Biscuit::getName); // Ensure Biscuit has getName class_("Chocolate") .def("getName", &Chocolate::getName); // Ensure Chocolate has getName class_("Factory", no_init) .def("getInstance", &Factory::getInstance, return_value_policy()) .staticmethod("getInstance") .def("makeFood", &Factory::makeFood, return_value_policy()); } Here's the complete source code of the C++ Factory Pattern... We will have to make a shared object (so) from this C++ project. /* * Food.h * Created on: Mar 10, 2021 * Author: som / #ifndef FOOD_H_ #define FOOD_H_ #include using namespace std; class Food { public: virtual string getName() = 0; virtual ~Food(){ } }; #endif / FOOD_H_ / / * Chocolate.h * Created on: Mar 10, 2021 * Author: som / #ifndef CHOCOLATE_H_ #define CHOCOLATE_H_ #include #include "Food.h" class Chocolate: public Food { public: Chocolate(); virtual ~Chocolate(); string getName(); }; #endif / CHOCOLATE_H_ / / * Chocolate.cpp * Created on: Mar 10, 2021 * Author: som */ #include "Chocolate.h" Chocolate::Chocolate() { // TODO Auto-generated constructor stub cout

Mar 13, 2025 - 04:31

Connecting C++ to Python using Boost.Python...

Many modern C++ applications provide a Python interface because it combines performance (C++) with ease of use (Python). Here’s why this trend has become so popular:

✔ It allows rapid prototyping.
✔ It combines speed (C++) with flexibility (Python).
✔ Python is popular in AI, ML, and scientific computing.
✔ Users can extend software via Python scripting.
Boost.Python is a powerful library that enables seamless integration between C++ and Python. It allows C++ functions and classes to be exposed to Python, enabling direct interaction between the two languages.

As I was playing around with Boost.Python, I made my existing Factory Pattern project written in C++ to expose itself to the python using Boost.Python library.

The most important part is the following lines of code. This is kind of self explanatory - how we expose the C++ classes and methods to Python code.

// Expose Singleton Factory to Python

BOOST_PYTHON_MODULE(FactoryPattern) {

    using namespace boost::python;

    class_<Food, boost::noncopyable>("Food", no_init)

        .def("getName", pure_virtual(&Food::getName));

    class_<Biscuit, bases<Food>>("Biscuit")

           .def("getName", &Biscuit::getName); // Ensure Biscuit has getName

    class_<Chocolate, bases<Food>>("Chocolate")

           .def("getName", &Chocolate::getName); // Ensure Chocolate has getName

    class_<Factory, boost::noncopyable>("Factory", no_init)

        .def("getInstance", &Factory::getInstance, return_value_policy<reference_existing_object>())

        .staticmethod("getInstance")

        .def("makeFood", &Factory::makeFood, return_value_policy<manage_new_object>());

}

Here's the complete source code of the C++ Factory Pattern... We will have to make a shared object (so) from this C++ project.

/*

 * Food.h

 *  Created on: Mar 10, 2021

 *      Author: som

 */

#ifndef FOOD_H_

#define FOOD_H_

#include 

using namespace std;

class Food {

public:
    virtual string getName() = 0;

    virtual ~Food(){
    }

};

#endif /* FOOD_H_ */

/*

 * Chocolate.h

 *  Created on: Mar 10, 2021

 *      Author: som

 */

#ifndef CHOCOLATE_H_

#define CHOCOLATE_H_

#include 

#include "Food.h"

class Chocolate: public Food {

public:

    Chocolate();

    virtual ~Chocolate();

    string getName();

};

#endif /* CHOCOLATE_H_ */

/*

 * Chocolate.cpp

 *  Created on: Mar 10, 2021

 *      Author: som

 */

#include "Chocolate.h"

Chocolate::Chocolate() {

    // TODO Auto-generated constructor stub

    cout<<"Chocolate is made..."<<endl;

}

Chocolate::~Chocolate() {

    // TODO Auto-generated destructor stub

}

string Chocolate::getName(){

    return "It's a Chocolate";

}

/*

 * Biscuit.h

 *  Created on: Mar 10, 2021

 *      Author: som

 */

#ifndef BISCUIT_H_

#define BISCUIT_H_

#include "Food.h"

class Biscuit: public Food {

public:

    Biscuit();

    string getName();

    ~Biscuit();

};

#endif /* BISCUIT_H_ */

/*

 * Biscuit.cpp

 *  Created on: Mar 10, 2021

 *      Author: som

 */

#include 

#include "Biscuit.h"

using namespace std;

Biscuit::Biscuit() {

    // TODO Auto-generated constructor stub

    cout<<"Biscuit is made..."<<endl;
}

Biscuit::~Biscuit(){}

string Biscuit::getName(){

    return "It's a Biscuit";

}
/*

 * Factory.h

 *  Created on: Mar 10, 2021

 *      Author: som

 */

#ifndef FACTORY_H_

#define FACTORY_H_

#include 

#include 

#include 

#include "Biscuit.h"

#include "Chocolate.h"

using namespace std;

class Factory{

public:

    static Factory* instance;

    static Factory* getInstance();



    Food* makeFood(const string& type);

private:
    Factory(){}

    // Delete copy constructor & assignment operator (Singleton pattern)

    Factory(const Factory&) = delete;

    Factory& operator=(const Factory&) = delete;

};

#endif /* FACTORY_H_ */

/*

 * Factory.cpp

 *  Created on: Jan 30, 2025

 *      Author: som

 */

#include "Factory.h"

Factory* Factory::instance = NULL;

Factory* Factory:: getInstance(){

        if(Factory::instance == NULL){

            Factory::instance = new Factory();

        }

        return Factory::instance;

    }

Food* Factory::makeFood(const string& type){

        if(type.compare("bi") == 0){

            return new Biscuit();

        }

        if(type.compare("ch") == 0){

            return new Chocolate();

        }

        return NULL;
    }

// Expose Singleton Factory to Python

BOOST_PYTHON_MODULE(FactoryPattern) {

    using namespace boost::python;

    class_<Food, boost::noncopyable>("Food", no_init)

        .def("getName", pure_virtual(&Food::getName));

    class_<Biscuit, bases<Food>>("Biscuit")

           .def("getName", &Biscuit::getName); // Ensure //Biscuit has getName


    class_<Chocolate, bases<Food>>("Chocolate")
           .def("getName", &Chocolate::getName); // Ensure Chocolate has getName

    class_<Factory, boost::noncopyable>("Factory", no_init)

        .def("getInstance", &Factory::getInstance, return_value_policy<reference_existing_object>())

        .staticmethod("getInstance")

        .def("makeFood", &Factory::makeFood, return_value_policy<manage_new_object>());

}

Here is the eclipse project settings...

and

And here's the python script to access the C++ methods.

import FactoryPattern

factory = FactoryPattern.Factory.getInstance()

biscuit = factory.makeFood("bi")
print(biscuit.getName())  # Expected: "Biscuit"

chocolate = factory.makeFood("ch")
print(chocolate.getName())  # Expected: "Chocolate"

Jai Hind... Jai Bharat...
By the way... there is another way to connect your Python code
to C++ - that is SWIG...