Flexible indexes: add Index base class and xindexes properties

doc/whats-new.rst

@@ -171,7 +171,10 @@ Internal Changes
   ``pytest.raises(Exception, match="foo")``;
   (:pull:`5188`), (:pull:`5191`).
   By `Maximilian Roos <https://github.com/max-sixty>`_.
-
+- Explicit indexes refactor: add an ``xarray.Index`` base class and
+  ``Dataset.xindexes`` / ``DataArray.xindexes`` properties. Also rename
+  ``PandasIndexAdapter`` to ``PandasIndex``, which now inherits from
+  ``xarray.Index`` (:pull:`5102`). By `Benoit Bovy <https://github.com/benbovy>`_.
 
 .. _whats-new.0.17.0:
 

xarray/core/dataarray.py

@@ -776,7 +776,7 @@ def encoding(self, value: Mapping[Hashable, Any]) -> None:
     def indexes(self) -> Indexes:
         """Mapping of pandas.Index objects used for label based indexing.
 
-        Raises an error in case where this Dataset has indexes that cannot be coerced
+        Raises an error if this Dataset has indexes that cannot be coerced
         to pandas.Index objects.
 
         See Also

xarray/core/dataset.py

@@ -1611,7 +1611,7 @@ def identical(self, other: "Dataset") -> bool:
     def indexes(self) -> Indexes:
         """Mapping of pandas.Index objects used for label based indexing.
 
-        Raises an error in case where this Dataset has indexes that cannot be coerced
+        Raises an error if this Dataset has indexes that cannot be coerced
         to pandas.Index objects.
 
         See Also

xarray/core/indexes.py

@@ -28,7 +28,7 @@
 class Index:
     """Base class inherited by all xarray-compatible indexes."""
 
-    __slots__ = "coord_names"
+    __slots__ = ("coord_names",)
 
     def __init__(self, coord_names: Union[Hashable, Iterable[Hashable]]):
         if isinstance(coord_names, Iterable) and not isinstance(coord_names, str):
@@ -183,9 +183,7 @@ def transpose(self, order) -> pd.Index:
         return self.array  # self.array should be always one-dimensional
 
     def __repr__(self) -> str:
-        return "{}(array={!r}, dtype={!r})".format(
-            type(self).__name__, self.array, self.dtype
-        )
+        return f"{type(self).__name__}(array={self.array!r}, dtype={self.dtype!r})"
 
     def copy(self, deep: bool = True) -> "PandasIndex":
         # Not the same as just writing `self.array.copy(deep=deep)`, as