Altair unable to chart pd.Series and integer column names

[HarvsG]

#matplot/pandas code
%matplotlib inline
star_wars.iloc[:,9:15].mean().plot.bar()

#equivalent altair code
means = star_wars.iloc[:,9:15].mean().to_frame().reset_index() 
#this line is needed as altair needs an index and cannot take pd.Series

means = sums.rename(columns={0:'mean_ranking'}) 
# since df.reset_index() given unamed columns int headers, which altair cant handle, the column must be renamed

alt.Chart(means).mark_bar().encode(
    x = 'index:N',
    y = 'mean_ranking' #not '0:Q'
)

If one does not rename the column the following error occurs

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
~/anaconda3/lib/python3.6/site-packages/altair/vegalite/v2/api.py in to_dict(self, *args, **kwargs)
    396         copy = self.copy()
    397         original_data = getattr(copy, 'data', Undefined)
--> 398         copy.data = _prepare_data(original_data, context)
    399 
    400         if original_data is not Undefined:

~/anaconda3/lib/python3.6/site-packages/altair/vegalite/v2/api.py in _prepare_data(data, context)
     90     # consolidate inline data to top-level datasets
     91     if data_transformers.consolidate_datasets:
---> 92         data = _consolidate_data(data, context)
     93 
     94     # if data is still not a recognized type, then return

~/anaconda3/lib/python3.6/site-packages/altair/vegalite/v2/api.py in _consolidate_data(data, context)
     57 
     58     if values is not Undefined:
---> 59         name = _dataset_name(values)
     60         data = core.NamedData(name=name, **kwds)
     61         context.setdefault('datasets', {})[name] = values

~/anaconda3/lib/python3.6/site-packages/altair/vegalite/v2/api.py in _dataset_name(values)
     33     if isinstance(values, core.InlineDataset):
     34         values = values.to_dict()
---> 35     values_json = json.dumps(values, sort_keys=True)
     36     hsh = hashlib.md5(values_json.encode()).hexdigest()
     37     return 'data-' + hsh

~/anaconda3/lib/python3.6/json/__init__.py in dumps(obj, skipkeys, ensure_ascii, check_circular, allow_nan, cls, indent, separators, default, sort_keys, **kw)
    236         check_circular=check_circular, allow_nan=allow_nan, indent=indent,
    237         separators=separators, default=default, sort_keys=sort_keys,
--> 238         **kw).encode(obj)
    239 
    240 

~/anaconda3/lib/python3.6/json/encoder.py in encode(self, o)
    197         # exceptions aren't as detailed.  The list call should be roughly
    198         # equivalent to the PySequence_Fast that ''.join() would do.
--> 199         chunks = self.iterencode(o, _one_shot=True)
    200         if not isinstance(chunks, (list, tuple)):
    201             chunks = list(chunks)

~/anaconda3/lib/python3.6/json/encoder.py in iterencode(self, o, _one_shot)
    255                 self.key_separator, self.item_separator, self.sort_keys,
    256                 self.skipkeys, _one_shot)
--> 257         return _iterencode(o, 0)
    258 
    259 def _make_iterencode(markers, _default, _encoder, _indent, _floatstr,

TypeError: '<' not supported between instances of 'int' and 'str'

it seems this might be the wide-form, long-form problem rearing it's head?

[jakevdp]

This has been addressed in master in #1107