CLN: make MultiIndex._shallow_copy signature match other subclasses (#37985)

Author: jbrockmendel

pandas/core/indexes/base.py

@@ -3986,7 +3986,11 @@ def _join_monotonic(self, other, how="left", return_indexers=False):
         else:
             return join_index
 
-    def _wrap_joined_index(self, joined, other):
+    def _wrap_joined_index(
+        self: _IndexT, joined: np.ndarray, other: _IndexT
+    ) -> _IndexT:
+        assert other.dtype == self.dtype
+
         if isinstance(self, ABCMultiIndex):
             name = self.names if self.names == other.names else None
         else:
@@ -4188,7 +4192,7 @@ def _is_memory_usage_qualified(self) -> bool:
         """
         return self.is_object()
 
-    def is_type_compatible(self, kind) -> bool:
+    def is_type_compatible(self, kind: str_t) -> bool:
         """
         Whether the index type is compatible with the provided type.
         """

pandas/core/indexes/datetimelike.py

@@ -403,6 +403,36 @@ def _format_attrs(self):
                 attrs.append(("freq", freq))
         return attrs
 
+    def _summary(self, name=None) -> str:
+        """
+        Return a summarized representation.
+
+        Parameters
+        ----------
+        name : str
+            Name to use in the summary representation.
+
+        Returns
+        -------
+        str
+            Summarized representation of the index.
+        """
+        formatter = self._formatter_func
+        if len(self) > 0:
+            index_summary = f", {formatter(self[0])} to {formatter(self[-1])}"
+        else:
+            index_summary = ""
+
+        if name is None:
+            name = type(self).__name__
+        result = f"{name}: {len(self)} entries{index_summary}"
+        if self.freq:
+            result += f"\nFreq: {self.freqstr}"
+
+        # display as values, not quoted
+        result = result.replace("'", "")
+        return result
+
     # --------------------------------------------------------------------
     # Indexing Methods
 
@@ -507,36 +537,6 @@ def where(self, cond, other=None):
         arr = self._data._from_backing_data(result)
         return type(self)._simple_new(arr, name=self.name)
 
-    def _summary(self, name=None) -> str:
-        """
-        Return a summarized representation.
-
-        Parameters
-        ----------
-        name : str
-            Name to use in the summary representation.
-
-        Returns
-        -------
-        str
-            Summarized representation of the index.
-        """
-        formatter = self._formatter_func
-        if len(self) > 0:
-            index_summary = f", {formatter(self[0])} to {formatter(self[-1])}"
-        else:
-            index_summary = ""
-
-        if name is None:
-            name = type(self).__name__
-        result = f"{name}: {len(self)} entries{index_summary}"
-        if self.freq:
-            result += f"\nFreq: {self.freqstr}"
-
-        # display as values, not quoted
-        result = result.replace("'", "")
-        return result
-
     def shift(self, periods=1, freq=None):
         """
         Shift index by desired number of time frequency increments.

pandas/core/indexes/datetimes.py

@@ -814,8 +814,8 @@ def slice_indexer(self, start=None, end=None, step=None, kind=None):
 
     # --------------------------------------------------------------------
 
-    def is_type_compatible(self, typ) -> bool:
-        return typ == self.inferred_type or typ == "datetime"
+    def is_type_compatible(self, kind: str) -> bool:
+        return kind == self.inferred_type or kind == "datetime"
 
     @property
     def inferred_type(self) -> str:

pandas/core/indexes/multi.py

@@ -1065,53 +1065,26 @@ def _engine(self):
 
     @property
     def _constructor(self):
-        return MultiIndex.from_tuples
+        return type(self).from_tuples
 
     @doc(Index._shallow_copy)
-    def _shallow_copy(
-        self,
-        values=None,
-        name=lib.no_default,
-        levels=None,
-        codes=None,
-        sortorder=None,
-        names=lib.no_default,
-    ):
-        if names is not lib.no_default and name is not lib.no_default:
-            raise TypeError("Can only provide one of `names` and `name`")
-        elif names is lib.no_default:
-            names = name if name is not lib.no_default else self.names
+    def _shallow_copy(self, values=None, name=lib.no_default):
+        names = name if name is not lib.no_default else self.names
 
         if values is not None:
-            assert levels is None and codes is None
-            return MultiIndex.from_tuples(values, sortorder=sortorder, names=names)
+            return type(self).from_tuples(values, sortorder=None, names=names)
 
-        levels = levels if levels is not None else self.levels
-        codes = codes if codes is not None else self.codes
-
-        result = MultiIndex(
-            levels=levels,
-            codes=codes,
-            sortorder=sortorder,
+        result = type(self)(
+            levels=self.levels,
+            codes=self.codes,
+            sortorder=None,
             names=names,
             verify_integrity=False,
         )
         result._cache = self._cache.copy()
         result._cache.pop("levels", None)  # GH32669
         return result
 
-    def symmetric_difference(self, other, result_name=None, sort=None):
-        # On equal symmetric_difference MultiIndexes the difference is empty.
-        # Therefore, an empty MultiIndex is returned GH13490
-        tups = Index.symmetric_difference(self, other, result_name, sort)
-        if len(tups) == 0:
-            return MultiIndex(
-                levels=[[] for _ in range(self.nlevels)],
-                codes=[[] for _ in range(self.nlevels)],
-                names=tups.name,
-            )
-        return type(self).from_tuples(tups, names=tups.name)
-
     # --------------------------------------------------------------------
 
     def copy(
@@ -1177,12 +1150,18 @@ def copy(
             if codes is None:
                 codes = deepcopy(self.codes)
 
-        new_index = self._shallow_copy(
+        levels = levels if levels is not None else self.levels
+        codes = codes if codes is not None else self.codes
+
+        new_index = type(self)(
             levels=levels,
             codes=codes,
-            names=names,
             sortorder=self.sortorder,
+            names=names,
+            verify_integrity=False,
         )
+        new_index._cache = self._cache.copy()
+        new_index._cache.pop("levels", None)  # GH32669
 
         if dtype:
             warnings.warn(
@@ -3612,6 +3591,18 @@ def _convert_can_do_setop(self, other):
 
         return other, result_names
 
+    def symmetric_difference(self, other, result_name=None, sort=None):
+        # On equal symmetric_difference MultiIndexes the difference is empty.
+        # Therefore, an empty MultiIndex is returned GH13490
+        tups = Index.symmetric_difference(self, other, result_name, sort)
+        if len(tups) == 0:
+            return type(self)(
+                levels=[[] for _ in range(self.nlevels)],
+                codes=[[] for _ in range(self.nlevels)],
+                names=tups.name,
+            )
+        return type(self).from_tuples(tups, names=tups.name)
+
     # --------------------------------------------------------------------
 
     @doc(Index.astype)

pandas/core/indexes/period.py

@@ -250,7 +250,7 @@ def __new__(
 
     @property
     def values(self) -> np.ndarray:
-        return np.asarray(self)
+        return np.asarray(self, dtype=object)
 
     def _maybe_convert_timedelta(self, other):
         """

pandas/core/indexes/timedeltas.py

@@ -229,8 +229,8 @@ def _maybe_cast_slice_bound(self, label, side: str, kind):
 
     # -------------------------------------------------------------------
 
-    def is_type_compatible(self, typ) -> bool:
-        return typ == self.inferred_type or typ == "timedelta"
+    def is_type_compatible(self, kind: str) -> bool:
+        return kind == self.inferred_type or kind == "timedelta"
 
     @property
     def inferred_type(self) -> str: