Computing class variable on demand?

[fortepianissimo]

Thanks Steve - actually my question was simpler than that. I just
wanted to use Daniels' recipe of lazy initialization on objects with
__slots__:

class Lazy(object):
    def __init__(self, calculate_function):
        self._calculate = calculate_function

    def __get__(self, obj, _=None):
        if obj is None:
            return self
        value = self._calculate(obj)
        setattr(obj, self._calculate.func_name, value)
        return value


class SomeClass(object):

    __slots__ = 'someprop'

    @Lazy
    def someprop(self):
        print 'Actually calculating value'
        return 13


o = SomeClass()
print o.someprop
print o.someprop



Running the code above will produce:

Actually calculating value
Traceback (most recent call last):
  File "Lazy.py", line 26, in ?
    print o.someprop
  File "Lazy.py", line 11, in __get__
    setattr(obj, self._calculate.func_name, value)
AttributeError: 'SomeClass' object attribute 'someprop' is read-only


Removing the __slots__ statement, everything would run normally.

Is there any workaround?