subclassing.cpp

#include <iostream>

using namespace std;

class A {

    protected:

        int count;

    public:

        A(void) : count(0) {}

        int getCount(void) {
            return this->count;
        }

        void add(void) {
            this->count++;
        }

        void add2(void) {
            this->add();
            this->add();
        }

};

class B : public A {

    public:

        void add(void) {
            this->count++;
            this->count++;
        }

};

int main(int argc, char *argv[])
{
    A a;
    a.add2();
    cout << "a.count = " << a.getCount() << endl;
    // a.count = 2

    B b;
    b.add2();
    cout << "b.count = " << b.getCount() << endl;
    // b.count = 2

    return 0;
}

subclassing.py

class A(object):

    def __init__(self):
        self.count = 0

    def add(self):
        self.count += 1

    def add2(self):
        self.add()
        self.add()


class B(A):

    def add(self):
        self.count += 2


if __name__ == '__main__':
    a = A()
    a.add2()
    print 'a.count =', a.count
    # a.count = 2

    b = B()
    b.add2()
    print 'b.count =', b.count
    # b.count = 4