Hi.
I have a problem with weak refs and bound methods. The best explanation for the
problem is a short bit of code. I have the three classes Wrapper, Foo and Bar:
import weakref
class Wrapper(object):
def __init__(self,x):
self.x = weakref.ref(x)
def __call__(self,*args,**kwargs):
x = self.x()
if x is None:
print "lost reference"
else:
return x(*args,**kwargs)
class Foo(object):
def __init__(self):
self._methods = set()
self._methods.add(Wrapper(self._foo))
def _foo(self):
print "_foo"
def callMethods(self):
for method in self._methods:
method()
def __del__(self):
print "del Foo"
class Bar(object):
def __init__(self):
self._methods = set()
self._methods.add(self._foo)
def _foo(self):
print "_foo"
def callMethods(self):
for method in self._methods:
method()
def __del__(self):
print "del Bar"
Now look what happens when I do this:
>>> f=Foo()
>>> f.callMethods()
lost reference
>>> del f
del Foo
>>> b=Bar()
>>> b.callMethods()
_foo
>>> del b
>>>
Foo looses the reference to its method but Bar on the other hand has a refloop
and
never gets deleted.
Does anyone know what happens here? How can I write such classes without
refloop and
without lost reference?
I'm using:
Python 2.5.1 (r251:54863, May 2 2007, 16:56:35)
[GCC 4.1.2 (Ubuntu 4.1.2-0ubuntu4)] on linux2
-panzi
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