Eyal Lotem 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]. 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
I don't know what you're trying to get at with this example. There isn't
any cyclic GC involved at all, just referencing counting. And before the
module globals are cleared, running_file is still referenced, so calling
its __del__ method early would be an outright error in the interpreter
(as far as I know, getting __del__ methods to run is one of the
*reasons* for clearing the module globals).
It's a fact of Python development: __del__ methods cannot safely
reference module globals, because those globals may be gone by the time
that method is invoked.
Cheers,
Nick.
--
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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