mis6 at pitt.edu
Wed Jul 23 23:11:47 CEST 2003
Steven Taschuk <staschuk at telusplanet.net> wrote in message news:<mailman.1058833821.16631.python-list at python.org>...
> Quoth Michele Simionato:
> > Steven Taschuk <staschuk at telusplanet.net> wrote in message news:<mailman.1058723911.12956.python-list at python.org>...
> > > _the_instance = None
> > > class MySingleton(object):
> > > def __new__(self):
> > > global _the_instance
> > > if _the_instance is None:
> > > _the_instance = object.__new__(self)
> > > return _the_instance
> > Why are you using a global here and not [a class attribute]
> The memory of that thread a little while back about using __del__
> with singletons. If the instance is referenced by a class
> attribute, the cyclic reference prevents the __del__ from being
> used. If the cycle goes through a module attribute, though, the
> zapping of module dicts during shutdown breaks the cycle and lets
> the __del__ run. (Whether all this is true depends on the version
> of Python, I think, but I don't know the details.)
> This might be relevant to the OP, whose example was a singleton
> representing the single database connection used by an entire
> application -- in such a case, __del__ would be a natural place to
> make sure the connection is closed properly.
> I should have explained this bit of trickery. :(
Thanks for the explation, I missed that thread.
More information about the Python-list