[ArrayManager] Add Series._as_manager (consolidate with DataFrame) (#40304)

Author: jorisvandenbossche

pandas/core/frame.py

@@ -68,7 +68,6 @@
     IndexKeyFunc,
     IndexLabel,
     Level,
-    Manager,
     NpDtype,
     PythonFuncType,
     Renamer,
@@ -745,25 +744,6 @@ def __init__(
 
         NDFrame.__init__(self, mgr)
 
-    def _as_manager(self, typ: str) -> DataFrame:
-        """
-        Private helper function to create a DataFrame with specific manager.
-
-        Parameters
-        ----------
-        typ : {"block", "array"}
-
-        Returns
-        -------
-        DataFrame
-            New DataFrame using specified manager type. Is not guaranteed
-            to be a copy or not.
-        """
-        new_mgr: Manager
-        new_mgr = mgr_to_mgr(self._mgr, typ=typ)
-        # fastpath of passing a manager doesn't check the option/manager class
-        return DataFrame(new_mgr)
-
     # ----------------------------------------------------------------------
 
     @property

pandas/core/generic.py

@@ -297,6 +297,25 @@ def _from_mgr(cls, mgr: Manager):
         object.__setattr__(obj, "_attrs", {})
         return obj
 
+    def _as_manager(self: FrameOrSeries, typ: str) -> FrameOrSeries:
+        """
+        Private helper function to create a DataFrame with specific manager.
+
+        Parameters
+        ----------
+        typ : {"block", "array"}
+
+        Returns
+        -------
+        DataFrame
+            New DataFrame using specified manager type. Is not guaranteed
+            to be a copy or not.
+        """
+        new_mgr: Manager
+        new_mgr = mgr_to_mgr(self._mgr, typ=typ)
+        # fastpath of passing a manager doesn't check the option/manager class
+        return self._constructor(new_mgr).__finalize__(self)
+
     # ----------------------------------------------------------------------
     # attrs and flags
 

pandas/core/internals/construction.py

@@ -73,13 +73,17 @@
     get_objs_combined_axis,
     union_indexes,
 )
-from pandas.core.internals.array_manager import ArrayManager
+from pandas.core.internals.array_manager import (
+    ArrayManager,
+    SingleArrayManager,
+)
 from pandas.core.internals.blocks import (
     ensure_block_shape,
     new_block,
 )
 from pandas.core.internals.managers import (
     BlockManager,
+    SingleBlockManager,
     create_block_manager_from_arrays,
     create_block_manager_from_blocks,
 )
@@ -213,15 +217,21 @@ def mgr_to_mgr(mgr, typ: str):
         if isinstance(mgr, BlockManager):
             new_mgr = mgr
         else:
-            new_mgr = arrays_to_mgr(
-                mgr.arrays, mgr.axes[0], mgr.axes[1], mgr.axes[0], typ="block"
-            )
+            if mgr.ndim == 2:
+                new_mgr = arrays_to_mgr(
+                    mgr.arrays, mgr.axes[0], mgr.axes[1], mgr.axes[0], typ="block"
+                )
+            else:
+                new_mgr = SingleBlockManager.from_array(mgr.arrays[0], mgr.index)
     elif typ == "array":
         if isinstance(mgr, ArrayManager):
             new_mgr = mgr
         else:
-            arrays = [mgr.iget_values(i).copy() for i in range(len(mgr.axes[0]))]
-            new_mgr = ArrayManager(arrays, [mgr.axes[1], mgr.axes[0]])
+            if mgr.ndim == 2:
+                arrays = [mgr.iget_values(i).copy() for i in range(len(mgr.axes[0]))]
+                new_mgr = ArrayManager(arrays, [mgr.axes[1], mgr.axes[0]])
+            else:
+                new_mgr = SingleArrayManager([mgr.internal_values()], [mgr.index])
     else:
         raise ValueError(f"'typ' needs to be one of {{'block', 'array'}}, got '{typ}'")
     return new_mgr

pandas/tests/internals/test_managers.py

@@ -8,6 +8,8 @@
 from pandas.core.internals import (
     ArrayManager,
     BlockManager,
+    SingleArrayManager,
+    SingleBlockManager,
 )
 
 
@@ -41,3 +43,30 @@ def test_dataframe_creation():
     assert isinstance(result._mgr, BlockManager)
     tm.assert_frame_equal(result, df_array)
     assert len(result._mgr.blocks) == 2
+
+
+def test_series_creation():
+
+    with pd.option_context("mode.data_manager", "block"):
+        s_block = pd.Series([1, 2, 3], name="A", index=["a", "b", "c"])
+    assert isinstance(s_block._mgr, SingleBlockManager)
+
+    with pd.option_context("mode.data_manager", "array"):
+        s_array = pd.Series([1, 2, 3], name="A", index=["a", "b", "c"])
+    assert isinstance(s_array._mgr, SingleArrayManager)
+
+    # also ensure both are seen as equal
+    tm.assert_series_equal(s_block, s_array)
+
+    # conversion from one manager to the other
+    result = s_block._as_manager("block")
+    assert isinstance(result._mgr, SingleBlockManager)
+    result = s_block._as_manager("array")
+    assert isinstance(result._mgr, SingleArrayManager)
+    tm.assert_series_equal(result, s_block)
+
+    result = s_array._as_manager("array")
+    assert isinstance(result._mgr, SingleArrayManager)
+    result = s_array._as_manager("block")
+    assert isinstance(result._mgr, SingleBlockManager)
+    tm.assert_series_equal(result, s_array)