issue_comments: 436015893

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https://github.com/pydata/xarray/issues/1077#issuecomment-436015893 https://api.github.com/repos/pydata/xarray/issues/1077 436015893 MDEyOklzc3VlQ29tbWVudDQzNjAxNTg5Mw== 7441788 2018-11-05T20:03:48Z 2018-11-05T20:03:48Z CONTRIBUTOR

This code isn't particularly pretty, and I'm not sure if it handles all cases, but it enables serialization of MultiIndex indices by calling ds.mi.encode_multiindices() before serializing and ds.mi.decode_multiindices() after deserializing.

``` @xr.register_dataset_accessor('mi') class MiscDatasetAccessor(): def init(self, xarray_obj): self._obj = xarray_obj

def encode_multiindices(self):
    result = self._obj
    for name, index in list(self._obj.indexes.items()):
        if isinstance(index, pd.MultiIndex):
            temp_name = '__' + name
            new_coords = {'{}__{}'.format(temp_name, level_name): level_values.rename(None)
                          for level_name, level_values in zip(index.names, index.levels)}
            new_coords[temp_name] = xr.DataArray(index.labels,
                                                 dims=('{}__names__'.format(temp_name),
                                                       '{}__num__'.format(temp_name)),
                                                 coords={'{}__names__'.format(temp_name): index.names,
                                                         '{}__num__'.format(temp_name): list(range(len(index)))},
                                                 attrs={'__is_multiindex': 1})
            result = result.drop(name).assign_coords(**new_coords)
    return result

def decode_multiindices(self):
    result = self._obj
    for temp_name, da in list(self._obj.coords.items()):
        if temp_name.startswith('__') and da.attrs.get('__is_multiindex', False):
            name = temp_name[2:]
            level_names = da.coords['{}__names__'.format(temp_name)].values
            levels = [result.coords['{}__{}'.format(temp_name, level_name)].values for level_name in level_names]
            labels = da.values
            result = result.assign_coords(**{name: pd.MultiIndex(levels=levels, labels=labels, names=level_names)})
            result = result.drop(['{}__{}'.format(temp_name, level_name) for level_name in level_names] +
                                 list(da.dims) + [temp_name])
    return result

```

 
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