[Python-Dev] Make it an error to use __slots__ with classic classes

[Raymond Hettinger]

Using __slots__ with a classic class is an error that does
not readily reveal itself.  For Py2.3.1, I would like to 
issue a warning, and for Py2.4, I would like to
raise an exception upon class creation:

>>> class A:
...    __slots__ = 'abc'   # Would otherwise pass silently
...    pass
...
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: PyClass_New: __slots__ only works with new-style classes


Do you guys agree?


Raymond Hettinger