Pickling dictionaries containing dictionaries: failing, recursion-style!

[lysdexia]

I'm having great fun playing with Markov chains. I am making a
dictionary of all the words in a given  string, getting a count of how
many appearances word1 makes in the string, getting a list of all the
word2s that follow each appearance of  word1 and a count of how many
times word2 appears in the string as well. (I know I should probably
be only counting how many times word2 actually follows word1, but as I
said, I'm having great fun playing ...)


printed output of the dictionary looks like so:

{'and': [1, {'to': 1}], 'down': [1, {'upon': 1}], 'them': [1, {'down':
1}], 'no': [1, {'others': 1}], 'this': [1, {'it': 1}], 'is': [2, {'a':
2}], 'upon': [1, {'a': 1}], 'it': [2, {'is': 2}], 'think': [2, {'and':
1, 'words': 1}], 'write': [1, {'this': 1}], 'to': [3, {'write': 1,
'put': 1, 'think': 1}], 'words': [1, {'no': 1}], 'others': [1,
{'think': 1}], 'put': [1, {'them': 1}], 'sin': [2, {'to': 2}]}

Here's the actual function.

def assembleVocab(self):
  self.wordDB = {}
  for word in self.words:
    try:
      if not word in self.wordDB.keys():
        wordsWeights = {}
        afterwords =  [self.words[i + 1] for i, e in
enumerate(self.words) if e == word]
        for aw in afterwords:
          if not aw in wordsWeights.keys():
            wordsWeights[aw] = afterwords.count(aw)
        self.wordDB[word] = [self.words.count(word), wordsWeights]
    except:
      pass
  out = open("mchain.pkl",'wb')
  pickle.dump(self.wordDB, out, -1)
  out.close()

My problem is, I can't seem to get it to unpickle. When I attempt to
load the
saved data, I get:

AttributeError: 'tuple' object has no attribute 'readline'

with pickle, and

TypeError: argument must have 'read' and 'readline' attributes

Looking at the pickle pages on docs.python.org, I see that I am
indeed
supposed to be able to pickle ``tuples, lists, sets, and dictionaries
containing only picklable objects''.

I'm sure I'm missing something obvious.  Clues?