check for uniqueness of multi-index level names

Author: Benoit Bovy

xarray/core/dataarray.py

@@ -68,6 +68,7 @@ def _infer_coords_and_dims(shape, coords, dims):
             new_coords[dim] = default_index_coordinate(dim, size)
 
     sizes = dict(zip(dims, shape))
+    level_names = {}
     for k, v in new_coords.items():
         if any(d not in dims for d in v.dims):
             raise ValueError('coordinate %s has dimensions %s, but these '
@@ -80,6 +81,15 @@ def _infer_coords_and_dims(shape, coords, dims):
                                  'length %s on the data but length %s on '
                                  'coordinate %r' % (d, sizes[d], s, k))
 
+        if v.ndim == 1:
+            idx_level_names = v.to_coord().level_names or []
+            for n in idx_level_names:
+                if n in level_names:
+                    raise ValueError('found duplicate MultiIndex level '
+                                     'name %r for coordinates %r and %r'
+                                     % (n, k, level_names[n]))
+                level_names[n] = k
+
     return new_coords, dims
 
 

xarray/core/dataset.py

@@ -224,6 +224,7 @@ def __init__(self, data_vars=None, coords=None, attrs=None,
             coords = {}
         if data_vars is not None or coords is not None:
             self._set_init_vars_and_dims(data_vars, coords, compat)
+            self._check_multiindex_level_names()
         if attrs is not None:
             self.attrs = attrs
         self._initialized = True
@@ -250,6 +251,21 @@ def _set_init_vars_and_dims(self, data_vars, coords, compat):
         self._coord_names = coord_names
         self._dims = dims
 
+    def _check_multiindex_level_names(self):
+        """Check for uniqueness of MultiIndex level names
+        """
+        level_names = {}
+        for c in self._coord_names:
+            v = self._variables[c]
+            if v.ndim == 1 and v._in_memory:
+                idx_level_names = v.to_coord().level_names or []
+                for n in idx_level_names:
+                    if n in level_names:
+                        raise ValueError('found duplicate MultiIndex level '
+                                         'name %r for coordinates %r and %r'
+                                         % (n, c, level_names[n]))
+                    level_names[n] = c
+
     @classmethod
     def load_store(cls, store, decoder=None):
         """Create a new dataset from the contents of a backends.*DataStore