title: how to modify parent class variable with the child class and use in another child class in python
body: <pre><code>class A(object):
      __A = None
      def get_a(self):
          return self.__A
      def set_a(self, value):
          self.__A = value
  
  class B(A):
      def method_b(self, value):
          self.set_a(value)
  
  class C(A):
      def method_c(self)
           self.get_a()
  </code></pre>
  
  <p>Someone can to explain me how can i to catch installed value in method_b inside my 'C' class method? </p>
  
  <p>P.S. In this variant i just getting nothing.</p>