[Zope] Storing Persistent Objects as keys in BTrees

[Thomas Guettler]

Hi have problem that appears at random:

I store Persistent Objects (inherited from a Zope Folder) as keys in a 
OOBTree.
I  developed something like mxmRelation 
(http://www.zope.org/Members/maxm/productList/mxmRelations)

It is strange: I get "r" from the keys of the hash, but if I try to get 
it from the hash it fails.
This only happens sometimes.

  def tostring(self):
        "return string of the relations"
        result={}
        for r in self._tree.keys():
            result[r]=[]
            hash_back=self._tree.get(r, None)
            if hash_back==None:
                print "tostring(): ", r
                raise Exception, "Internal Error ???"
                return
            for r2 in hash_back.keys():
                result[r].append(r2)
        return result

It is a single threaded application

I use the version for win32:  
Zope 2.5.0 (binary release, python 2.1, win32-x86), python 2.1.2, win32