[ python-Bugs-998998 ] pickle bug - recursively memoizing class?

[SourceForge.net]

Bugs item #998998, was opened at 2004-07-27 22:55
Message generated for change (Comment added) made by grubert
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=998998&group_id=5470

Category: Python Library
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Skip Montanaro (montanaro)
Assigned to: Nobody/Anonymous (nobody)
Summary: pickle bug - recursively memoizing class?

Initial Comment:
The attached script (picklecycle.py) gives me an
assertion error
in Pickler.memoize().  Maybe I'm just doing something dumb.
I have very little experience with pickle and even less
experience
pickling new-style class instances.  I'm just trying to
adapt an
existing messy object graph to allow it to be pickled.
 I realize the
two instances refer to each other, but I thought pickle was
supposed to gracefully handle cyclic object graphs.

I can worm around the problem a couple ways.  First,
getting
rid of new-style classes does the trick.  Also
modifying B.__reduce__
to not return self.__dict__ seems to do the trick.

Output (cycle.out) and a modified version of
Pickler.memoize
(memoize.py) will be attached momentarily.


----------------------------------------------------------------------

Comment By: engelbert gruber (grubert)
Date: 2005-05-19 13:00

Message:
Logged In: YES 
user_id=147070

it does memoize recursively, 
but "asserts" not to get stuck in cycles.

that's how i understand the code if ::

        assert id(obj) not in self.memo

is replaced by ::

        if id(obj) in self.memo:
            return

it works (better). and test_pickle.py still passes.

----------------------------------------------------------------------

Comment By: Skip Montanaro (montanaro)
Date: 2004-07-27 22:57

Message:
Logged In: YES 
user_id=44345

Attaching the output I see when running picklecycle.py w/ the
modified memoize() method (cycle.out).

----------------------------------------------------------------------

Comment By: Skip Montanaro (montanaro)
Date: 2004-07-27 22:56

Message:
Logged In: YES 
user_id=44345

Attaching chatty version of Pickler.memoize()


----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=998998&group_id=5470