DEPR: CategoricalBlock; combine Block.replace methods (pandas-dev#40527)

Author: jbrockmendel

pandas/core/internals/__init__.py

@@ -9,7 +9,6 @@
 )
 from pandas.core.internals.blocks import (  # io.pytables, io.packers
     Block,
-    CategoricalBlock,
     DatetimeBlock,
     DatetimeTZBlock,
     ExtensionBlock,
@@ -28,7 +27,6 @@
 
 __all__ = [
     "Block",
-    "CategoricalBlock",
     "NumericBlock",
     "DatetimeBlock",
     "DatetimeTZBlock",
@@ -48,3 +46,18 @@
     "create_block_manager_from_arrays",
     "create_block_manager_from_blocks",
 ]
+
+
+def __getattr__(name: str):
+    import warnings
+
+    if name == "CategoricalBlock":
+        warnings.warn(
+            "CategoricalBlock is deprecated and will be removed in a future version. "
+            "Use ExtensionBlock instead.",
+            FutureWarning,
+            stacklevel=2,
+        )
+        return ExtensionBlock
+
+    raise AttributeError(f"module 'pandas.core.internals' has no attribute '{name}'")

pandas/core/internals/blocks.py

@@ -673,6 +673,7 @@ def copy(self, deep: bool = True):
     # ---------------------------------------------------------------------
     # Replace
 
+    @final
     def replace(
         self,
         to_replace,
@@ -687,15 +688,30 @@ def replace(
         """
         inplace = validate_bool_kwarg(inplace, "inplace")
 
+        # Note: the checks we do in NDFrame.replace ensure we never get
+        #  here with listlike to_replace or value, as those cases
+        #  go through _replace_list
+
+        values = self.values
+
+        if isinstance(values, Categorical):
+            # TODO: avoid special-casing
+            blk = self if inplace else self.copy()
+            blk.values.replace(to_replace, value, inplace=True)
+            return [blk]
+
+        regex = should_use_regex(regex, to_replace)
+
+        if regex:
+            return self._replace_regex(to_replace, value, inplace=inplace)
+
         if not self._can_hold_element(to_replace):
             # We cannot hold `to_replace`, so we know immediately that
             #  replacing it is a no-op.
             # Note: If to_replace were a list, NDFrame.replace would call
             #  replace_list instead of replace.
             return [self] if inplace else [self.copy()]
 
-        values = self.values
-
         mask = missing.mask_missing(values, to_replace)
         if not mask.any():
             # Note: we get here with test_replace_extension_other incorrectly
@@ -720,7 +736,7 @@ def replace(
         else:
             # split so that we only upcast where necessary
             return self.split_and_operate(
-                type(self).replace, to_replace, value, inplace=inplace, regex=regex
+                type(self).replace, to_replace, value, inplace=True, regex=regex
             )
 
     @final
@@ -1223,7 +1239,7 @@ def take_nd(
         Take values according to indexer and return them as a block.bb
 
         """
-        # algos.take_nd dispatches for DatetimeTZBlock, CategoricalBlock
+        # algos.take_nd dispatches for DatetimeTZBlock
         # so need to preserve types
         # sparse is treated like an ndarray, but needs .get_values() shaping
 
@@ -1422,7 +1438,7 @@ class ExtensionBlock(Block):
     Notes
     -----
     This holds all 3rd-party extension array types. It's also the immediate
-    parent class for our internal extension types' blocks, CategoricalBlock.
+    parent class for our internal extension types' blocks.
 
     ExtensionArrays are limited to 1-D.
     """
@@ -1579,7 +1595,6 @@ def take_nd(
 
     def _can_hold_element(self, element: Any) -> bool:
         # TODO: We may need to think about pushing this onto the array.
-        # We're doing the same as CategoricalBlock here.
         return True
 
     def _slice(self, slicer):
@@ -2019,41 +2034,6 @@ def _maybe_downcast(self, blocks: List[Block], downcast=None) -> List[Block]:
     def _can_hold_element(self, element: Any) -> bool:
         return True
 
-    def replace(
-        self,
-        to_replace,
-        value,
-        inplace: bool = False,
-        regex: bool = False,
-    ) -> List[Block]:
-        # Note: the checks we do in NDFrame.replace ensure we never get
-        #  here with listlike to_replace or value, as those cases
-        #  go through _replace_list
-
-        regex = should_use_regex(regex, to_replace)
-
-        if regex:
-            return self._replace_regex(to_replace, value, inplace=inplace)
-        else:
-            return super().replace(to_replace, value, inplace=inplace, regex=False)
-
-
-class CategoricalBlock(ExtensionBlock):
-    __slots__ = ()
-
-    def replace(
-        self,
-        to_replace,
-        value,
-        inplace: bool = False,
-        regex: bool = False,
-    ) -> List[Block]:
-        inplace = validate_bool_kwarg(inplace, "inplace")
-        result = self if inplace else self.copy()
-
-        result.values.replace(to_replace, value, inplace=True)
-        return [result]
-
 
 # -----------------------------------------------------------------
 # Constructor Helpers
@@ -2116,7 +2096,7 @@ def get_block_type(values, dtype: Optional[Dtype] = None):
         # Need this first(ish) so that Sparse[datetime] is sparse
         cls = ExtensionBlock
     elif isinstance(dtype, CategoricalDtype):
-        cls = CategoricalBlock
+        cls = ExtensionBlock
     elif vtype is Timestamp:
         cls = DatetimeTZBlock
     elif vtype is Interval or vtype is Period:

pandas/core/internals/managers.py

@@ -67,7 +67,6 @@
 )
 from pandas.core.internals.blocks import (
     Block,
-    CategoricalBlock,
     DatetimeTZBlock,
     ExtensionBlock,
     ObjectValuesExtensionBlock,
@@ -1867,13 +1866,6 @@ def _form_blocks(
         object_blocks = _simple_blockify(items_dict["ObjectBlock"], np.object_)
         blocks.extend(object_blocks)
 
-    if len(items_dict["CategoricalBlock"]) > 0:
-        cat_blocks = [
-            new_block(array, klass=CategoricalBlock, placement=i, ndim=2)
-            for i, array in items_dict["CategoricalBlock"]
-        ]
-        blocks.extend(cat_blocks)
-
     if len(items_dict["ExtensionBlock"]):
         external_blocks = [
             new_block(array, klass=ExtensionBlock, placement=i, ndim=2)

pandas/tests/internals/test_api.py

@@ -26,7 +26,6 @@ def test_namespace():
     ]
     expected = [
         "Block",
-        "CategoricalBlock",
         "NumericBlock",
         "DatetimeBlock",
         "DatetimeTZBlock",

pandas/tests/io/test_common.py

@@ -258,6 +258,7 @@ def test_read_expands_user_home_dir(
             ),
         ],
     )
+    @pytest.mark.filterwarnings("ignore:CategoricalBlock is deprecated:FutureWarning")
     def test_read_fspath_all(self, reader, module, path, datapath):
         pytest.importorskip(module)
         path = datapath(*path)

pandas/tests/io/test_feather.py

@@ -20,6 +20,7 @@
 
 @filter_sparse
 @pytest.mark.single
+@pytest.mark.filterwarnings("ignore:CategoricalBlock is deprecated:FutureWarning")
 class TestFeather:
     def check_error_on_write(self, df, exc, err_msg):
         # check that we are raising the exception

pandas/tests/io/test_parquet.py

@@ -573,6 +573,7 @@ def test_write_column_index_nonstring(self, pa):
         self.check_error_on_write(df, engine, ValueError, msg)
 
 
+@pytest.mark.filterwarnings("ignore:CategoricalBlock is deprecated:FutureWarning")
 class TestParquetPyArrow(Base):
     def test_basic(self, pa, df_full):