#!/usr/local/bin/python3
from types import MethodType

class A(object):
  def __init__(self):
    self.a = 1

class B(A):
  def __init__(self):
    self._a = 0
    super(A, self).__init__()
    self.a = MethodType(a, self)

  def r(self):
    self.a = 2

def a(self):
  return self._a 

print(B().a())