pickle error: can't pickle instancemethod objects

[Michele Simionato]

Can somebody explain what's happening with the following script?

$ echo example.py
import pickle

class Example(object):

    def __init__(self, obj, registry):
        self._obj = obj
        self._registry = registry
        for name, func in self._registry.iteritems():
            setattr(self, name, func.__get__(obj, obj.__class__))

    def __gestate__(self): # should skip the bound methods attributes
        return dict(_registry=self._registry, _obj=self._obj)

class C(object):
    pass

def foo(self):
    pass

if __name__ == '__main__':
    ex = Example(C(), dict(foo=foo))
    pickle.dumps(ex)

I get the following traceback:

Traceback (most recent call last):
  File "pickle_error.py", line 22, in <module>
    pickle.dumps(ex)
  File "/usr/lib/python2.5/pickle.py", line 1366, in dumps
    Pickler(file, protocol).dump(obj)
  File "/usr/lib/python2.5/pickle.py", line 224, in dump
    self.save(obj)
  File "/usr/lib/python2.5/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/usr/lib/python2.5/pickle.py", line 419, in save_reduce
    save(state)
  File "/usr/lib/python2.5/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.5/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.5/pickle.py", line 663, in _batch_setitems
    save(v)
  File "/usr/lib/python2.5/pickle.py", line 306, in save
    rv = reduce(self.proto)
  File "/usr/lib/python2.5/copy_reg.py", line 69, in _reduce_ex
    raise TypeError, "can't pickle %s objects" % base.__name__
TypeError: can't pickle instancemethod objects

I know that instancemethods cannot be pickled, this is why I
used a __getstate__ method, but apparently it does not work.
Any hint?

           Michele Simionato