strange behaviour at termination time

Fredrik Lundh fredrik at pythonware.com
Mon Jun 28 15:48:56 CEST 1999


Fabien COUTANT <fabien.coutant at steria.fr> wrote:
> Basically there is a base class name that I found bound to None,
> which prevents me to call base methods.
> 
> I tested it with 1.5.1 on Linux and 1.5.2 on Windows. Was working
> fine with 1.4 in Debian/Linux 1.3.1 till I upgraded to Debian 2.1...
> 
> Bug or feature ? Quite annoying if feature...

feature.

1.5.2 does a more aggressive global clean-up when the
interpreter is shut down.  this includes zapping modules
and module globals, and replacing them with references
to None.

> More that it, I discovered during testing that sometimes it is correct
> if I change the base class name !

namespaces are dictionaries.  changing the name may or may
not change the clean-up order...

> Here is sample code to show it:
> 
> ----------------------------------
> class A :
>     def __del__ (self) :
>         print "A.__del__", self
> 
> class B (A) :
>     def __del__ (self) :
>         print "B.__del__", self, A
>         # can't do A.__del__ (self) for example
> 
> x = A ()
> y = B ()
> ----------------------------------
> 
> In this configuration it should show ok.
> If you change the name of the first class from A to X everywhere
> then X is bound to None in B.__del__ !!!

the only reasonable way to get around this is to explicitly
bind all the names you want in your destructor:

>     def __del__ (self, A=A) :
>         print "B.__del__", self, A
>         A.__del__(self)

(btw, 1.4 probably didn't call B's destructor at all...)

</F>





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