class MyDescriptorClass(object):
    def __init__(self, owner, name, activates = 0):
        self.value = None
        self.name = name
        self.owner = owner
        self.activates = 0
        self.connects = []

    def __set__(self, obj, val):
        self.set(val)
    def __get__(self, instance, owner):
        return self.value

    def set(self, value):
        if self.value  == value:
            return 0
        self.value = value
        if self.activates:
            self.owner.evaluate()

    def connect(self, inputs):
        if not isinstance(inputs, list):
            inputs = list(inputs)
        for input in inputs:
            self.connects.append(input)

class ParentClass(object):
    def __init__(self, name):
        self.states = {}
        self.name = name
        self.A = MyDescriptorClass(self, name, activates = 1)
        self.B = MyDescriptorClass(self, name, activates = 1)
        self.states.setDefault('A', self.A)
        self.states.setDefault('B', self.B)

class ChildClass1(ParentClass):
    def __init__(self, name)
        super(ChildClass1, self).__init__(name)
        self.ans = None
    def evaluate(self):
        self.ans = self.A.value + self.B.value

class ChildClass2(ParentClass):
    def __init__(self, name)
        super(ChildClass1, self).__init__(name)
        self.ans = None
    def evaluate(self):
        self.ans = self.A.value * self.B.value

class ParentClass(object):
    A = MyDescriptorClass() # here I am unable to pass the owner

c = ChildClass1("c1")
  c.A = 10 # I directly want to set this value instead of using c.A.set(10)
  c.B = 20
  c.evaluate()
  print c.ans # 30
  c.B = 40
  print c.ans # 50

class MyDescriptorClass(object):
    def __init__(self, activates = 0):
        self.value = None
        self.activates = activates
        self.connects = []

    def __set__(self, instance, val):      # 1
        if self.value == val:
            return 0
        self.value = val
        if self.activates:
            instance.evaluate()
    def __get__(self, instance, instcls):  # 1
        return self.value

class GateInput(object):
    def __init__(self, index):
        self.index = index                    # 4

    def __get__(self, inst, instcls):
        return inst.inputs[self.index].ans    # 5

    def __set__(self, inst, val):
        if isinstance(val, (float, int)):
            inst.inputs[self.index] = Constant(val)
        else:
            inst.inputs[self.index] = val


class Constant(object):
    def __init__(self, val):
        self.ans = val


class Gate(object):
    A = GateInput(0)               # 1
    B = GateInput(1)               # 1

    def __init__(self, name):
        self.name = name
        self.inputs = [Constant(0), Constant(0)]    # 2


class Adder(Gate):
    @property
    def ans(self):
        result = 0
        for gate in self.inputs:
            result += gate.ans                      # 3
        return result


class Multiplier(Gate):
    @property
    def ans(self):
        result = 1
        for gate in self.inputs:
            result *= gate.ans
        return result

b = Multiplier('b1')
b.A = 2
b.B = 3
print(b.A)
# 2
print(b.ans)
# 6

c = Adder('c1')
c.A = 10
print(c.ans)
# 10

# This connects output of b to an input of c
c.B = b
print(c.ans)
# 16

class MyDescriptorClass(object):
    def __init__(self):
        self.data = defaultDict(dict)
    def configure(self, owner, name, activates = 0):
        container = self.data(id(owner))
        container["value"] = None
        container["name"] = name
        ...

    def __set__(self, owner, value):
        # implemnt your previous "set" method straight here
        ...
        ...