hello.cpp

#include <iostream>
using namespace std;

class A {
public:
  char a;
  int i;
  A (int i, char a) {
    this->i = i;
    this->a = a;
  }
};


class B {
public:
  int i;
  char a;
  B (int i, char a) {
    this->i = i;
    this->a = a;
  }
};

int main() {
  A * var = new A(1, 'a');
  cout << "A.i = " << var->i << endl;
  B * var2 = (B *) var;
  cout << "B.i = " << var2->i << endl;
  
  return 0;
}

hello.py

class A(object):
    def my1(self):
        print "my1"

class B(object):
    def my2(self):
        print "my2"


if __name__ == '__main__':
    obj_name = raw_input()
    locals()[obj_name]().my1()