CLN: unify NumpyBlock, ObjectBlock, and NumericBlock (pandas-dev#52817)

* CLN: unify NumpyBlock, ObjectBlock, and NumericBlock

* CLN: respond to review comments

* CLN: deprecate ObjectBlock and NumericBlock

* CLN: appease mypy

* CLN: remove out-of-date reference to maybe_split

* CLN: respond to review comments

* CLN: remove NumpyBlock from the semi-public API

* CLN: test for is_numeric in block internals tests

Author: ngoldbaum

pandas/core/internals/__init__.py

@@ -11,8 +11,6 @@
     Block,
     DatetimeTZBlock,
     ExtensionBlock,
-    NumericBlock,
-    ObjectBlock,
 )
 from pandas.core.internals.concat import concatenate_managers
 from pandas.core.internals.managers import (
@@ -23,10 +21,8 @@
 
 __all__ = [
     "Block",
-    "NumericBlock",
     "DatetimeTZBlock",
     "ExtensionBlock",
-    "ObjectBlock",
     "make_block",
     "DataManager",
     "ArrayManager",
@@ -38,3 +34,27 @@
     # this is preserved here for downstream compatibility (GH-33892)
     "create_block_manager_from_blocks",
 ]
+
+
+def __getattr__(name: str):
+    import warnings
+
+    from pandas.util._exceptions import find_stack_level
+
+    if name in ["NumericBlock", "ObjectBlock"]:
+        warnings.warn(
+            f"{name} is deprecated and will be removed in a future version. "
+            "Use public APIs instead.",
+            DeprecationWarning,
+            stacklevel=find_stack_level(),
+        )
+        if name == "NumericBlock":
+            from pandas.core.internals.blocks import NumericBlock
+
+            return NumericBlock
+        else:
+            from pandas.core.internals.blocks import ObjectBlock
+
+            return ObjectBlock
+
+    raise AttributeError(f"module 'pandas.core.internals' has no attribute '{name}'")

pandas/core/internals/blocks.py

@@ -469,13 +469,36 @@ def convert(
         using_cow: bool = False,
     ) -> list[Block]:
         """
-        attempt to coerce any object types to better types return a copy
-        of the block (if copy = True) by definition we are not an ObjectBlock
-        here!
+        Attempt to coerce any object types to better types. Return a copy
+        of the block (if copy = True).
         """
-        if not copy and using_cow:
-            return [self.copy(deep=False)]
-        return [self.copy()] if copy else [self]
+        if not self.is_object:
+            if not copy and using_cow:
+                return [self.copy(deep=False)]
+            return [self.copy()] if copy else [self]
+
+        if self.ndim != 1 and self.shape[0] != 1:
+            return self.split_and_operate(Block.convert, copy=copy, using_cow=using_cow)
+
+        values = self.values
+        if values.ndim == 2:
+            # the check above ensures we only get here with values.shape[0] == 1,
+            # avoid doing .ravel as that might make a copy
+            values = values[0]
+
+        res_values = lib.maybe_convert_objects(
+            values,  # type: ignore[arg-type]
+            convert_non_numeric=True,
+        )
+        refs = None
+        if copy and res_values is values:
+            res_values = values.copy()
+        elif res_values is values and using_cow:
+            refs = self.refs
+
+        res_values = ensure_block_shape(res_values, self.ndim)
+        res_values = maybe_coerce_values(res_values)
+        return [self.make_block(res_values, refs=refs)]
 
     # ---------------------------------------------------------------------
     # Array-Like Methods
@@ -680,7 +703,7 @@ def _replace_regex(
         List[Block]
         """
         if not self._can_hold_element(to_replace):
-            # i.e. only ObjectBlock, but could in principle include a
+            # i.e. only if self.is_object is True, but could in principle include a
             #  String ExtensionBlock
             if using_cow:
                 return [self.copy(deep=False)]
@@ -1273,7 +1296,7 @@ def fillna(
     ) -> list[Block]:
         """
         fillna on the block with the value. If we fail, then convert to
-        ObjectBlock and try again
+        block to hold objects instead and try again
         """
         # Caller is responsible for validating limit; if int it is strictly positive
         inplace = validate_bool_kwarg(inplace, "inplace")
@@ -2064,7 +2087,7 @@ def _unstack(
         needs_masking: npt.NDArray[np.bool_],
     ):
         # ExtensionArray-safe unstack.
-        # We override ObjectBlock._unstack, which unstacks directly on the
+        # We override Block._unstack, which unstacks directly on the
         # values of the array. For EA-backed blocks, this would require
         # converting to a 2-D ndarray of objects.
         # Instead, we unstack an ndarray of integer positions, followed by
@@ -2100,6 +2123,7 @@ def _unstack(
 
 class NumpyBlock(libinternals.NumpyBlock, Block):
     values: np.ndarray
+    __slots__ = ()
 
     @property
     def is_view(self) -> bool:
@@ -2118,10 +2142,28 @@ def get_values(self, dtype: DtypeObj | None = None) -> np.ndarray:
     def values_for_json(self) -> np.ndarray:
         return self.values
 
+    @cache_readonly
+    def is_numeric(self) -> bool:  # type: ignore[override]
+        dtype = self.values.dtype
+        kind = dtype.kind
+
+        return kind in "fciub"
+
+    @cache_readonly
+    def is_object(self) -> bool:  # type: ignore[override]
+        return self.values.dtype.kind == "O"
+
 
 class NumericBlock(NumpyBlock):
+    # this Block type is kept for backwards-compatibility
+    # TODO(3.0): delete and remove deprecation in __init__.py.
+    __slots__ = ()
+
+
+class ObjectBlock(NumpyBlock):
+    # this Block type is kept for backwards-compatibility
+    # TODO(3.0): delete and remove deprecation in __init__.py.
     __slots__ = ()
-    is_numeric = True
 
 
 class NDArrayBackedExtensionBlock(libinternals.NDArrayBackedBlock, EABackedBlock):
@@ -2257,49 +2299,6 @@ class DatetimeTZBlock(DatetimeLikeBlock):
     values_for_json = NDArrayBackedExtensionBlock.values_for_json
 
 
-class ObjectBlock(NumpyBlock):
-    __slots__ = ()
-    is_object = True
-
-    @maybe_split
-    def convert(
-        self,
-        *,
-        copy: bool = True,
-        using_cow: bool = False,
-    ) -> list[Block]:
-        """
-        attempt to cast any object types to better types return a copy of
-        the block (if copy = True) by definition we ARE an ObjectBlock!!!!!
-        """
-        if self.dtype != _dtype_obj:
-            # GH#50067 this should be impossible in ObjectBlock, but until
-            #  that is fixed, we short-circuit here.
-            if using_cow:
-                return [self.copy(deep=False)]
-            return [self]
-
-        values = self.values
-        if values.ndim == 2:
-            # maybe_split ensures we only get here with values.shape[0] == 1,
-            # avoid doing .ravel as that might make a copy
-            values = values[0]
-
-        res_values = lib.maybe_convert_objects(
-            values,
-            convert_non_numeric=True,
-        )
-        refs = None
-        if copy and res_values is values:
-            res_values = values.copy()
-        elif res_values is values and using_cow:
-            refs = self.refs
-
-        res_values = ensure_block_shape(res_values, self.ndim)
-        res_values = maybe_coerce_values(res_values)
-        return [self.make_block(res_values, refs=refs)]
-
-
 # -----------------------------------------------------------------
 # Constructor Helpers
 
@@ -2358,10 +2357,8 @@ def get_block_type(dtype: DtypeObj) -> type[Block]:
     kind = dtype.kind
     if kind in "Mm":
         return DatetimeLikeBlock
-    elif kind in "fciub":
-        return NumericBlock
 
-    return ObjectBlock
+    return NumpyBlock
 
 
 def new_block_2d(

pandas/tests/extension/base/casting.py

@@ -4,7 +4,7 @@
 import pandas.util._test_decorators as td
 
 import pandas as pd
-from pandas.core.internals import ObjectBlock
+from pandas.core.internals.blocks import NumpyBlock
 from pandas.tests.extension.base.base import BaseExtensionTests
 
 
@@ -16,7 +16,9 @@ def test_astype_object_series(self, all_data):
         result = ser.astype(object)
         assert result.dtype == np.dtype(object)
         if hasattr(result._mgr, "blocks"):
-            assert isinstance(result._mgr.blocks[0], ObjectBlock)
+            blk = result._mgr.blocks[0]
+            assert isinstance(blk, NumpyBlock)
+            assert blk.is_object
         assert isinstance(result._mgr.array, np.ndarray)
         assert result._mgr.array.dtype == np.dtype(object)
 
@@ -26,7 +28,8 @@ def test_astype_object_frame(self, all_data):
         result = df.astype(object)
         if hasattr(result._mgr, "blocks"):
             blk = result._mgr.blocks[0]
-            assert isinstance(blk, ObjectBlock), type(blk)
+            assert isinstance(blk, NumpyBlock), type(blk)
+            assert blk.is_object
         assert isinstance(result._mgr.arrays[0], np.ndarray)
         assert result._mgr.arrays[0].dtype == np.dtype(object)
 

pandas/tests/frame/test_block_internals.py

@@ -20,10 +20,7 @@
     option_context,
 )
 import pandas._testing as tm
-from pandas.core.internals import (
-    NumericBlock,
-    ObjectBlock,
-)
+from pandas.core.internals.blocks import NumpyBlock
 
 # Segregated collection of methods that require the BlockManager internal data
 # structure
@@ -387,7 +384,8 @@ def test_constructor_no_pandas_array(self):
         result = DataFrame({"A": arr})
         expected = DataFrame({"A": [1, 2, 3]})
         tm.assert_frame_equal(result, expected)
-        assert isinstance(result._mgr.blocks[0], NumericBlock)
+        assert isinstance(result._mgr.blocks[0], NumpyBlock)
+        assert result._mgr.blocks[0].is_numeric
 
     def test_add_column_with_pandas_array(self):
         # GH 26390
@@ -400,8 +398,10 @@ def test_add_column_with_pandas_array(self):
                 "c": pd.arrays.PandasArray(np.array([1, 2, None, 3], dtype=object)),
             }
         )
-        assert type(df["c"]._mgr.blocks[0]) == ObjectBlock
-        assert type(df2["c"]._mgr.blocks[0]) == ObjectBlock
+        assert type(df["c"]._mgr.blocks[0]) == NumpyBlock
+        assert df["c"]._mgr.blocks[0].is_object
+        assert type(df2["c"]._mgr.blocks[0]) == NumpyBlock
+        assert df2["c"]._mgr.blocks[0].is_object
         tm.assert_frame_equal(df, df2)
 
 

pandas/tests/internals/test_api.py

@@ -27,10 +27,8 @@ def test_namespace():
     ]
     expected = [
         "Block",
-        "NumericBlock",
         "DatetimeTZBlock",
         "ExtensionBlock",
-        "ObjectBlock",
         "make_block",
         "DataManager",
         "ArrayManager",

pandas/tests/series/test_constructors.py

@@ -46,7 +46,7 @@
     IntervalArray,
     period_array,
 )
-from pandas.core.internals.blocks import NumericBlock
+from pandas.core.internals.blocks import NumpyBlock
 
 
 class TestSeriesConstructors:
@@ -2098,7 +2098,8 @@ def test_constructor_no_pandas_array(self, using_array_manager):
         result = Series(ser.array)
         tm.assert_series_equal(ser, result)
         if not using_array_manager:
-            assert isinstance(result._mgr.blocks[0], NumericBlock)
+            assert isinstance(result._mgr.blocks[0], NumpyBlock)
+            assert result._mgr.blocks[0].is_numeric
 
     @td.skip_array_manager_invalid_test
     def test_from_array(self):