AssertionError in pickle's memoize function

[Michael Hohn]

Hi,
here is a code sample that shows the problem I ran into:
test.py:
=================================
import pickle
class aList(list):
   def __init__(self, arg):
       # w/o this call, pickle works...
       list.__init__(self, arg)
       pass
A = aList([1,2])
B = aList([A, 3])
the_data = {'a': A, 'b': B}
A._stored_by = the_data
pickle.dumps([the_data, B])             # ok
pickle.dumps([B, the_data])             # fails
=================================
Outputs under:
Python 2.3 (#1, Sep 13 2003, 00:49:11)
[GCC 3.3 20030304 (Apple Computer, Inc. build 1495)] on darwin
9 scarlet::~:0> python test.py
Traceback (most recent call last):
 File "test.py", line 16, in ?
   pickle.dumps([B, the_data])             # fails
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 1386, in dumps
   Pickler(file, protocol, bin).dump(obj)
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 231, in dump
   self.save(obj)
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 293, in save
   f(self, obj) # Call unbound method with explicit self
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 614, in save_list
   self._batch_appends(iter(obj))
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 629, in _batch_appends
   save(x)
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 338, in save
   self.save_reduce(obj=obj, *rv)
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 419, in save_reduce
   self.memoize(obj)
 File 
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/p
ickle.py", line 251, in memoize
   assert id(obj) not in self.memo
AssertionError

with the same problem under python on linux:
Python 2.3 (#1, Jul 31 2003, 14:19:24)
[GCC 2.96 20000731 (Red Hat Linux 7.3 2.96-113)] on linux2
Traceback (most recent call last):
 File "<stdin>", line 1, in ?
 File "/usr/tmp/python-286703ll", line 1, in ?
   pickle.dumps([B, the_data])             # fails
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 1386, 
in dumps
   Pickler(file, protocol, bin).dump(obj)
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 231, in 
dump
   self.save(obj)
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 293, in 
save
   f(self, obj) # Call unbound method with explicit self
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 614, in 
save_list
   self._batch_appends(iter(obj))
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 629, in 
_batch_appends
   save(x)
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 338, in 
save
   self.save_reduce(obj=obj, *rv)
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 419, in 
save_reduce
   self.memoize(obj)
 File "/usr/local_cci/Python-2.3/lib/python2.3/pickle.py", line 251, in 
memoize
   assert id(obj) not in self.memo
AssertionError


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