On 5/4/07, Guido van Rossum <[EMAIL PROTECTED]> wrote:
> On 5/4/07, Steven Bethard <[EMAIL PROTECTED]> wrote:
> > On 5/4/07, Guido van Rossum <[EMAIL PROTECTED]> wrote:
> > > Hm, a thought just occurred to me. Why not arrange for object.__new__
> > > to call [the moral equivalent of] weakref.cleanup(self,
> > > self.__class__.__del__), and get rid of the direct call to __del__
> > > from the destructor? (And the special-casing of objects with __del__
> > > in the GC module, of course.)
> >
> > That seems like a good idea, though I'm still a little unclear as to
> > how far the AttrMap should be going to look like a real instance. As
> > it stands, you can only access items from the instance __dict__. That
> > means no methods, class attributes, etc.::
>
> Oh, you mean 'self' as passed to the callback is not the instance?
> That kills the whole idea (since the typical __del__ calls
> self.flush() or self.close()).
>
[..snip example using __dict__..]
>
> If it really has to be done this way, I think the whole PEP is doomed.
Any attempt that keeps the entire contents of __dict__ alive is
doomed. It's likely to contain a cycle back to the original object,
and avoiding that is the whole point of jumping through these hoops.
I've got a metaclass that moves explicitly marked attributes and
methods into a "core" object, allowing you to write code like this:
class MyFile(safedel):
__coreattrs__ = ['_fd']
def __init__(self, path):
super(MyFile, self).__init__()
self._fd = os.open(path, ...)
@coremethod
def __safedel__(core):
core.close()
@coremethod
def close(core):
# This method is written to be idempotent
if core._fd is not None:
os.close(core._fd)
core._fd = None
I've submitted it to the python cookbook, but I don't know how long
it'll take to get posted; it's a little on the long side at 163 lines.
The biggest limitation is you can't easily use super() in core
methods, although the proposed changes to super() would probably fix
this.
--
Adam Olsen, aka Rhamphoryncus
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