Armin Rigo wrote:
> Hello Jim,
>
> On Wed, Jun 30, 2004 at 10:24:26AM -0400, Jim Fulton wrote:
>
>>Here is a demonstration Python implementation:
>>
>> from threading import currentThread
>>
>> class local(object):
>>
>> ...
>
>
> The instance should clear the entry from all the per-thread dictionaries when
> it is deallocated,
Ugh. Now you want me to work hard. ;)
...
>
> Descriptor fun! I think there is a way to write this class so that "regular"
> attributes like __class__ still work, and without having to special-case
> __dict__. Something along the lines of:
>
> def __patch(self):
> key = "thread-local-%x" % id(self)
> d = currentThread().__dict__.setdefault(key, {})
> object.__setattr__(self, '__dict__', d)
>
> def __getattribute__(self, name):
> self.__patch()
> return super(local, self).__getattribute__(name)
>
> def __setattr__(self, name, value):
> self.__patch()
> super(local, self).__setattr__(name, value)
>
> I am unclear about how C types should do the equivalent of the 'super' call,
> though. But I'm ok with declaring that we don't care and use
> PyObject_Generic[GS]etAttr().
Note that this makes it go somewhat slower, since we now have to
search the class dictionary as well as the instance dictonary.
I don't think it's worth it to avoid special handling for __dict__
and __class__.
This approach *does* provide the benefit that you can subclass
thead.local to ad default values, methods, and descriptors, which
I think could be very useful. I'll investigate this.
The easiest way to do this in C will be to have different logic
for the base class and for subclasses. For the base class,
I'll do what I'm doing now (adding handling for __class__).
For subclasses, I'll do what you suggest. This mans that
simple usages of the base class don't get the extra performance
hit.
>
> Finally, don't forget __delattr__.
Yup.
Thanks.
Jim
--
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