Pickling Objects inherited from dict (Bug?)

[Thomas Guettler]

Hi!

After unpickling the objects are not the same
any more. Is this a bug or feature?

import pickle

class MyDictContainer(dict):
    def __init__(self):
        dict.__init__(self)
        print "MyDictContainer.__init__"

class MyDict(dict):
    def __init__(self, root, name):
        dict.__init__(self)
        self.root=root
        self.name=name

container=MyDictContainer()
for name in ["one", "two", "three"]:
    mydict=MyDict(container, name)
    container[name]=mydict
    
print container
file="data.pickle"
fd=open(file, "w")
pickle.dump(container, fd)
fd.close()

fd=open(file)
unpickle=pickle.load(fd)
fd.close()
print unpickle


Output:

===> python test-pickle.py
MyDictContainer.__init__
{'three': {}, 'two': {}, 'one': {}}
{'one': {}, 
 'three': (<class '__main__.MyDictContainer'>, 
   <type 'dict'>, {'three': {}, 
 'two': (<class '__main__.MyDictContainer'>, <type 'dict'>, 
   {'three': {}, 'two': {}, 'one': {}}), 'one': {}}), 'two': 
    (<class '__main__.MyDictContainer'>, <type 'dict'>,
    {'three': {}, 'two': {}, 'one': {}})}

After unpickling the object is not the same anymore.
Any hints?

If I inherit from UserDict instead, the is no error.

 thomas