Metaclass for attributes of specific type sets the attribute b to attribute name

scratch.py

class Meta(type):
    def __new__(cls, name, bases, attrs):
        for n, v in attrs.viewitems():
            if isinstance(v, E):
                v.b = n
        return super(Meta, cls).__new__(cls, name, bases, attrs)

class E(object):
    def __init__(self, a):
        self.a = a
        self.b = None

    def __repr__(self):
        return '{0.__class__.__name__}({0.a}, {0.b})'.format(self)

class C(object):
    __metaclass__ = Meta

    Aaa = E('1')
    Bbb = E('2')

# for attr, val in C.__dict__.items():
#     if isinstance(val, E):
#         val.b = attr