[Persistence-sig] "Straw Baby" Persistence API

[Jeremy Hylton]

>>>>> "SM" == Steve Menard <smenard@bigfoot.com> writes:

  >> > On a side note, as I have said in another post, I have done
  >> > exactly that, subclassing dict and list. While my model didn't
  >> > need to override __getitem__(), the __setitem__() at least
  >> > seemed to act properly. In fact the only problem I have found
  >> > is that it was not possible to mix __slots__ and dict/list.
  >>
  >> For all strange and perverse things I've done, slots work just
  >> fine when inheriting from list and dict.  Again, can you provide
  >> an example of where you found otherwise?

  SM> Ok, my problem was from inheriting both from dict and from my
  SM> Persistent class. Persistent was using slots. I could dig out or
  SM> reproduce error message if you're interested.

dict and Persistent are not compatible at the C level.  That's a
second problem, and one that I hadn't thought of.  (It doesn't have
anything to do with slots.)

>>> class PD(Persistent, dict):
...     pass
...
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: multiple bases have instance lay-out conflict

There's no way to make this problem go away if we continue to
implement persistence in C.

Jeremy