__slots__

[David Isaac]

"Ziga Seilnacht" <ziga.seilnacht at gmail.com> wrote:
> If you want to restrict  attribute asignment, you should use the
> __setattr__ special method, see:
> http://docs.python.org/ref/attribute-access.html

That "should" is what I am asking about. If I understand,
in the simplest case, you want me to say something like
        def __setattr__(self,name,value):
            if name in myattrlist:
                object.__setattr__(self,name,value)
            else:
                raise AttributeError
instead just saying
        __slots__ = myattrlist
I understand that this *is* the prevailing advice.  But why?


> >>> class A(object):
> ...     pass
> ...
> >>> class B(A):
> ...     __slots__ = ('spam',)
> ...
> >>> b = B()
> >>> b.eggs = 1
> >>> b.eggs
> 1

A good example of something that could be easily
missed, and possibly an answer to my question above.
(Although not I think if I am subclassing object.)

Thanks,
Alan Isaac