>>> d = pandas.Series({('1ab','2'): 3, ('1ab',3):4}, ) >>> d = pandas.concat([d,d]) >>> d = pandas.concat([d,d], axis=1) >>> pickle.loads(pickle.dumps(d)) 0 1 1ab 3 4 4 2 3 3 3 4 4 2 3 3 >>> pickle.loads(pickle.dumps(d.T)) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib64/python2.7/pickle.py", line 1382, in loads return Unpickler(file).load() File "/usr/lib64/python2.7/pickle.py", line 858, in load dispatch[key](self) File "/usr/lib64/python2.7/pickle.py", line 1217, in load_build setstate(state) File "venv/lib/python2.7/site-packages/pandas/core/internals.py", line 2063, in __setstate__ placement=self.axes[0].get_indexer(items)) File "venv/lib/python2.7/site-packages/pandas/core/index.py", line 3200, in get_indexer raise Exception('Reindexing only valid with uniquely valued Index ' Exception: Reindexing only valid with uniquely valued Index objects