Why do I have to call del explicitly for com objects?

[bg_ie at yahoo.com]

Gabriel Genellina skrev:

> <bg_ie at yahoo.com> escribió en el mensaje
> news:1169210578.544593.310100 at v45g2000cwv.googlegroups.com...
>
> > I'm creating objects in my python script belonging to a COM object
> > which I dispatch using win32com.client.DispatchEx. Hence, dllhost.dll
> > is the concerned process. The problem is that the objects destructor
> > within the com object is not called if the object lives past a certain
> > number of seconds. For example, this function will not call the
> > destructor concerned with obj unless the sleep is commented out.
> >
> > def fnction:
> >  obj = comobj.createACertainObject()
> >  obj.doStuff()
> >  sleep(10)
> >  obj.doMoreStuff()
> >  #del obj
>
> I don't understand the case.
> del does not invoke a destructor, just decrements the object's reference
> count. When the rc reaches zero, the object is a candidate for GC. That is,
> "some time in the future", the GC would destroy it (unless it's part of a
> circular reference chain...)
> So, *inside* your function, there is a reference held by the local variable
> obj. It is decremented automatically when you exit the function (and obj
> gets out of scope) or if you explicitely use del.
> You can use sys.getrefcount() to see how many references an object has. (The
> output is +1 because getrefcount() has a temporary reference to the object
> too).
>
> py> x="Hello World"
> py> sys.getrefcount(x)
> 2
>
> See how many references your obj have. After calling doStuff or doMoreStuff,
> you can have more references if those functions store `self` somewhere, or
> pass it to another method that does so.
>
> > It seems to me that the GC forgets about obj after a certain amount of
> > time. I can force the destructor to be called using del obj at the end
> > of my function, but why do I have to call this explicitly?
> If del obj works at the end, exiting the function should work too. Both ways
> you decrement the rc. There is something *more* in here.
>
> --
> Gabriel Genellina

Thanks for the reply. I tried using a longer sleep before the del but
the destructor wasn't called this time. I guess del is not the issue
here what so ever. As far as I can see, the garbage collector forgets
about my object after a certain period of time. The fix i'm using now
is to use Destruct functions in my CoM object which I call explicitly.

def fnction:
  obj = comobj.createACertainObject()
  obj.doStuff()
  sleep(10)
  obj.doMoreStuff()
  obj.Destruct()

I'd still love to know what the issue is here.

Thanks,

Barry.