REF: SingleBlockManager dont subclass BlockManager

pandas/_typing.py

@@ -185,5 +185,5 @@
 ]
 
 # internals
-Manager = Union["ArrayManager", "BlockManager"]
+Manager = Union["ArrayManager", "BlockManager", "SingleBlockManager"]
 SingleManager = Union["SingleArrayManager", "SingleBlockManager"]

pandas/core/frame.py

@@ -548,6 +548,7 @@ class DataFrame(NDFrame, OpsMixin):
     _HANDLED_TYPES = (Series, Index, ExtensionArray, np.ndarray)
     _accessors: set[str] = {"sparse"}
     _hidden_attrs: frozenset[str] = NDFrame._hidden_attrs | frozenset([])
+    _mgr: BlockManager | ArrayManager
 
     @property
     def _constructor(self) -> type[DataFrame]:
@@ -3518,6 +3519,25 @@ def _get_value(self, index, col, takeable: bool = False) -> Scalar:
         index = self.index.get_loc(index)
         return self._get_value(index, col, takeable=True)
 
+    def _get_item_cache(self, item):
+        """Return the cached item, item represents a label indexer."""
+        cache = self._item_cache
+        res = cache.get(item)
+        if res is None:
+            # All places that call _get_item_cache have unique columns,
+            #  pending resolution of GH#33047
+
+            loc = self.columns.get_loc(item)
+            values = self._mgr.iget(loc)
+            res = self._box_col_values(values, loc).__finalize__(self)
+
+            cache[item] = res
+            res._set_as_cached(item, self)
+
+            # for a chain
+            res._is_copy = self._is_copy
+        return res
+
     def __setitem__(self, key, value):
         key = com.apply_if_callable(key, self)
 

pandas/core/generic.py

@@ -3886,26 +3886,6 @@ class   animal   locomotion
     def __getitem__(self, item):
         raise AbstractMethodError(self)
 
-    @final
-    def _get_item_cache(self, item):
-        """Return the cached item, item represents a label indexer."""
-        cache = self._item_cache
-        res = cache.get(item)
-        if res is None:
-            # All places that call _get_item_cache have unique columns,
-            #  pending resolution of GH#33047
-
-            loc = self.columns.get_loc(item)
-            values = self._mgr.iget(loc)
-            res = self._box_col_values(values, loc).__finalize__(self)
-
-            cache[item] = res
-            res._set_as_cached(item, self)
-
-            # for a chain
-            res._is_copy = self._is_copy
-        return res
-
     def _slice(self: FrameOrSeries, slobj: slice, axis=0) -> FrameOrSeries:
         """
         Construct a slice of this container.