Establishing why an object can't be pickled

Question

I\'m receiving an object, t, from an api of type Object. I am unable to pickle it, getting the error:

  File \"p.py\", line 55, in          


        

Answer 1

I tried Dill but it didn't explain my issue. Instead, I used the following code from https://gist.github.com/andresriancho/15b5e226de68a0c2efd0, which happened to show a bug in my __getattribute__ override:

def debug_pickle(instance):
  """
  :return: Which attribute from this object can't be pickled?
  """
  attribute = None

  for k, v in instance.__dict__.iteritems():
      try:
          cPickle.dumps(v)
      except:
          attribute = k
          break

  return attribute

---

Edit: Here's a reproduction of my code, using pickle and cPickle:

class myDict(dict):

    def __getattribute__(self, item):
        # Try to get attribute from internal dict
        item = item.replace("_", "$")

        if item in self:
            return self[item]

        # Try super, which may leads to an AttribueError
        return super(myDict, self).__getattribute__(item)

myd = myDict()

try: 
    with open('test.pickle', 'wb') as myf:
        cPickle.dump(myd, myf, protocol=-1)
except:
    print traceback.format_exc()


try:
    with open('test.pickle', 'wb') as myf:
        pickle.dump(myd, myf, protocol=-1)
except:
    print traceback.format_exc()

Output:

Traceback (most recent call last):
File "/Users/myuser/Documents/workspace/AcceptanceTesting/ingest.py", line 35, in 
  cPickle.dump(myd, myf, protocol=-1)
UnpickleableError: Cannot pickle  objects

Traceback (most recent call last):
File "/Users/myuser/Documents/workspace/AcceptanceTesting/ingest.py", line 42, in 
  pickle.dump(myd, myf, protocol=-1)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1370, in dump
  Pickler(file, protocol).dump(obj)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 224, in dump
  self.save(obj)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 313, in save
  (t.__name__, obj))
PicklingError: Can't pickle 'myDict' object: {}

You'll see that the reason is because attribute names are being mangled by __getattribute__