__slot__ issues

[Arthur Siegel]

(The following is copy of my post to tutor at python.org.
Since I believe it to involve a (minor) bug issue, I
thought I'd copy it here for possible comment)

Apologies to the folks who do not share my new found interest in slots.

Which I am starting to think of as the quark of the Python object world.

>>> class A(object):
 __slots__=("a")
>>> class B(A):
 __slots__=("b")
>>> b=B()
>>> b.__slots__
'b'
>>> b.a=4
In other words "a" is somehow acting as a slot for
B instances, but is not *in* B.__slots__.
How would one then reference, introspect, whatever
as to what are in fact available slots for instances of B?

And a possibly minor bug:

>>> class A(object):
 __slots__="a"

>>> class B(object):
 pass

>>> class C(A,B):
 __slots__=("b")


>>> c=C()
>>> c.a=1
>>> c.b=2
>>> c.c=3
Traceback (most recent call last):
  File "<pyshell#12>", line 1, in ?
    c.c=3
SystemError: C:\Code\221\Objects\dictobject.c:511: bad argument to internal
function

If B is a classic class and I do the same multi-inheritance I get the
expected error message:

AttributeError: 'C' object has no attribute 'c'

So its the error message, not the behavior that I am pointing to as probably
unintended.

Art



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