class AttrSquare:
    def __init__(self, start):
        self.value = start                            # Triggers __setattr__!

    def __getattr__(self, attr):                      # On undefined attr fetch
        if attr == 'X':
            return self.value ** 2                    # value is not undefined
        else:
            raise AttributeError(attr)

    def __setattr__(self, attr, value):               # On all attr assignments
        if attr == 'X':
            attr = 'value'
        self.__dict__[attr] = value

A = AttrSquare(3)       # 2 instances of class with overloading
B = AttrSquare(32)      # Each has different state information

print(A.X)              # 3 ** 2
A.X = 4
print(A.X)              # 4 ** 2
print(B.X)              # 32 ** 2 (1024)