Magic values template

gistfile1.py

class MagicValue(object):
    def __eq__(self, obj):
        return type(self) is type(obj)

    def __nonzero__(self):
        return False

    def __hash__(self):
        return id(self)

    def __getnewargs__(self):
        return ()

    def __getstate__(self):
        return False


class _Unchanged(MagicValue):
    def __repr__(self):
        return 'Unchanged'

    def __contains__(self, _item):
        return False


class _Deleted(MagicValue):
    def __repr__(self):
        return 'Deleted'


Unchanged = _Unchanged()
Deleted = _Deleted()