On Jun 28, 6:32 pm, "Martin v. Löwis" <[EMAIL PROTECTED]> wrote: > > Example: > > > import os > > class RunningFile(object): > > filename = '/tmp/running' > > def __init__(self): > > open(self.filename, 'wb') > > def __del__(self): > > os.unlink(self.filename) > > running_file = RunningFile() > > > The deller object is in a cycle as described above [as well as the > > Deller class itself]. > > I think you are mistaken here. The RunningFile instance in above code > is *not* part of a cycle. It doesn't have any instance variables (i.e. > its __dict__ is empty), and it only refers to its class, which (AFAICT) > doesn't refer back to the instance.
As I explained above, it *is* part of a cycle: """including the class objects themselves: class->dict->function->func_globals""". Note: running_file.__class.__.__dict__['__init__'].func_globals['running_file'] is running_file. > > > When Python exits, it could call > > deller.__del__() and then collect the cycle. But Python does the wrong > > thing here, and gets rid of the globals before calling __del__: > > Exception exceptions.AttributeError: "'NoneType' object has no > > attribute 'unlink'" in <bound method RunningFile.__del__ of > > <__main__.RunningFile object at 0x7f9655eb92d0>> ignored > > This is a different issue. For shutdown, Python doesn't rely on > cyclic garbage collection (only). Instead, all modules get forcefully > cleared, causing this problem. I know. I assumed Python does not rely on cyclic garbage collectioin for shutdown, because it wouldn't work, as _all_ globals that have *any* instance method will be part of a cycle, and any of them which have a __del__ will not be collected. > > I believe applying the above enhancement would solve these problems. > > No, they wouldn't. > > To work around the real problem in your case, put everything that the > destructor uses into an instance or class attribute: > > class RunningFile(object): > filename = '/tmp/running' > _unlink = os.unlink > def __init__(self): > open(self.filename, 'wb') > def __del__(self): > self._unlink(self.filename) I *mentioned* this workaround. What I propose is not a workaround but a solution. You wouldn't need to clean up module globals ad-hoc'ishly, because the cyclic collection would collect your object, even with its __del__. > Regards, > Martin Please read my entire mail before replying to it. Thanks! Eyal > _______________________________________________ > Python-Dev mailing list > [EMAIL PROTECTED]://mail.python.org/mailman/listinfo/python-dev > Unsubscribe:http://mail.python.org/mailman/options/python-dev/python-dev2-garchiv... _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
