python pickle.dumps AssertionError

Question

I\'m trying to pickle a class instance containing two lists of another instances. The instances in the two lists have attributes that refer instances of each other. Here are

Answer 1

There are some kinds of data the older pickle protocol cannot handle. To solve your problem, use pickle.HIGHEST_PROTOCOL

>>> p = pickle.dumps(g)
  File "/usr/lib/python2.6/pickle.py", line 244, in memoize
    assert id(obj) not in self.memo
AssertionError:
>>> p = pickle.dumps(g, pickle.HIGHEST_PROTOCOL)
>>> # No problem!