refactored and fixed dim name / coord replacement

Author: Benoit Bovy

xarray/core/dataarray.py

@@ -90,12 +90,14 @@ def _remap_key(self, key):
             # expand the indexer so we can handle Ellipsis
             labels = indexing.expanded_indexer(key, self.data_array.ndim)
             key = dict(zip(self.data_array.dims, labels))
-
         return indexing.remap_label_indexers(self.data_array, key)
 
     def __getitem__(self, key):
         pos_indexers, new_indexes = self._remap_key(key)
-        return self.data_array[pos_indexers]._replace_indexes(new_indexes)
+        ds = self.data_array[pos_indexers]._to_temp_dataset()
+        return self.data_array._from_temp_dataset(
+            ds._replace_indexes(new_indexes)
+        )
 
     def __setitem__(self, key, value):
         pos_indexers, new_indexes = self._remap_key(key)
@@ -240,16 +242,6 @@ def _replace_maybe_drop_dims(self, variable, name=__default):
                                  if set(v.dims) <= allowed_dims)
         return self._replace(variable, coords, name)
 
-    def _replace_indexes(self, indexes):
-        obj = self
-        for dim, idx in iteritems(indexes):
-            if idx.name is None:
-                idx.name = dim + "_unnamed_level"
-            obj = obj.rename({dim: idx.name})
-            new_coord = Coordinate(idx.name, idx)
-            obj = obj._replace(coords={idx.name: new_coord})
-        return obj
-
     __this_array = _ThisArray()
 
     def _to_temp_dataset(self):
@@ -605,10 +597,10 @@ def sel(self, method=None, tolerance=None, **indexers):
         Dataset.sel
         DataArray.isel
         """
-        pos_indexers, new_indexes = indexing.remap_label_indexers(
-            self, indexers, method=method, tolerance=tolerance
+        ds = self._to_temp_dataset().sel(
+            method=method, tolerance=tolerance, **indexers
         )
-        return self.isel(**pos_indexers)._replace_indexes(new_indexes)
+        return self._from_temp_dataset(ds)
 
     def isel_points(self, dim='points', **indexers):
         """Return a new DataArray whose dataset is given by pointwise integer

xarray/core/dataset.py

@@ -420,20 +420,16 @@ def _replace_vars_and_dims(self, variables, coord_names=None,
         return obj
 
     def _replace_indexes(self, indexes):
-        obj = self
-        for dim, idx in iteritems(indexes):
-            if idx.name is None:
-                idx.name = dim + "_unnamed_level"
-            obj = obj.rename({dim: idx.name})
-            new_coord = Coordinate(idx.name, idx)
-            variables = OrderedDict()
-            for k, v in iteritems(obj._variables):
-                if k == idx.name:
-                    variables[k] = new_coord
-                else:
-                    variables[k] = v
-            obj = obj._replace_vars_and_dims(variables)
-        return obj
+        variables = OrderedDict()
+        for k, v in iteritems(self._variables):
+            if k in indexes.keys():
+                idx = indexes[k]
+                variables[k] = Coordinate(idx.name, idx)
+            else:
+                variables[k] = v
+        obj = self._replace_vars_and_dims(variables)
+        dim_names = {dim: idx.name for dim, idx in iteritems(indexes)}
+        return obj.rename(dim_names)
 
     def copy(self, deep=False):
         """Returns a copy of this dataset.