On 5/12/07, Guido van Rossum <[EMAIL PROTECTED]> wrote:
> On 5/12/07, Steven Bethard <[EMAIL PROTECTED]> wrote:
> > And here's a version that doesn't lose updates to the finalizer attributes:
> >
> > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/519635
> >
> > It replaces enable_finalizer() with a class attribute __finalattrs__.
> > >From __finalize__, all class attributes and methods are accessible, as
> > are any instance attributes specified by __finalattrs__. Guido's
> > BufferedWriter example looks like::
> >
> > class BufferedWriter(Finalized):
> > __finalattrs__ = 'buffer', 'raw'
> > ...
> > def flush(self):
> > self.raw.write(self.buffer)
> > self.buffer = b""
> >
> > def __finalize__(self):
> > self.flush()
>
> But can I subclass it and in the subclass override (extend) flush()? E.g.
>
> class MyWriter(BufferedWriter):
> def flush(self):
> super(MyWriter, self).flush() # Or super.flush() once PEP xxx is accepted
> print("Feel free to unplug the disk now")
Yep. The 'self' passed to __finalize__ is still an instance of the
same class (e.g. BufferedWriter or MyWriter). So inheritance works
normally:
>>> class BufferedWriter(Finalized):
... __finalattrs__ = 'buffer', 'raw'
... def __init__(self):
... self.buffer = ''
... self.raw = 'raw'
... def flush(self):
... print 'writing:', self.buffer, 'to', self.raw
... self.buffer = ''
... def __finalize__(self):
... self.flush()
...
>>> class MyWriter(BufferedWriter):
... def flush(self):
... super(MyWriter, self).flush()
... print 'feel free to unplug the disk now'
...
>>> w = MyWriter()
>>> del w
writing: to raw
feel free to unplug the disk now
STeVe
--
I'm not *in*-sane. Indeed, I am so far *out* of sane that you appear a
tiny blip on the distant coast of sanity.
--- Bucky Katt, Get Fuzzy
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