Pb with __del__ and inheritence

[Erwan Adam]

Hello all,

Can someone reproduce this bug ... I use :

[adam@is111902 /home/adam/Work/Python]python
Python 2.4.3 (#2, Sep 18 2006, 21:07:35)
[GCC 4.1.1 20060724 (prerelease) (4.1.1-3mdk)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.

>>>

First test :

[adam@is111902 /home/adam/Work/Python]cat bug_del.py && echo "------"
&& python bug_del.py

class XObject(object) :

def __del__(self):
print "XObject.__del_ _"
return

pass

class A(XObject):

def __del__(self):
print "A.__del__"
XObject.__del__ (self)
return

pass

a = A()
------
A.__del__
XObject.__del__
[adam@is111902 /home/adam/Work/Python]>

Everything is ok ... now I just replace "a = A()" by "aaa = A()":

[adam@is111902 /home/adam/Work/Python]cat bug_del.py && echo "------"
&& python bug_del.py

class XObject(object) :

def __del__(self):
print "XObject.__del_ _"
return

pass

class A(XObject):

def __del__(self):
print "A.__del__"
XObject.__del__ (self)
return

pass

aaa = A()
------
A.__del__
Exception exceptions.Attr ibuteError: "'NoneType' object has no attribute
'__del__'" in <bound method A.__del__ of <__main__.A object at
0xb7bb124c>igno red
[adam@is111902 /home/adam/Work/Python]>

!!!


Thanks in advance,

E.A.

[Gabriel Genellina]

Re: Pb with __del__ and inheritence

En Wed, 07 Mar 2007 07:35:05 -0300, Erwan Adam <erwan.adam@cea .fr>
escribió:

Can someone reproduce this bug ... I use :

Same on 2.5 Windows.

class XObject(object) :
>
def __del__(self):
print "XObject.__del_ _"
return
>
pass
>
class A(XObject):
>
def __del__(self):
print "A.__del__"
XObject.__del__ (self)
return
>
pass
>
aaa = A()
------
A.__del__
Exception exceptions.Attr ibuteError: "'NoneType' object has no attribute
'__del__'" in <bound method A.__del__ of <__main__.A object at
0xb7bb124c>igno red

Print XObject inside A.__del__ and you can see that it is None. That means
that the XObject reference was set to None *before* aaa was deleted.
Values inside the module namespace are set to None when it's destroyed (to
break possible reference cycles, I presume). I can't find any place in the
docs that guarantees any ordering on the object deletion, so I don't
consider this a "bug". See the big notes on the __del__ method docs.

If you *really* must do some cleanup on A.__del__, you can't trust on
*any* globals, and you must store a reference to anything needed inside
__del__

--
Gabriel Genellina