REF: implement PandasArray.pad_or_backfill (#53827)

Author: jbrockmendel

pandas/core/arrays/datetimelike.py

@@ -2235,7 +2235,7 @@ def interpolate(
         *,
         method,
         axis: int,
-        index: Index | None,
+        index: Index,
         limit,
         limit_direction,
         limit_area,
@@ -2255,7 +2255,7 @@ def interpolate(
         else:
             out_data = self._ndarray.copy()
 
-        missing.interpolate_array_2d(
+        missing.interpolate_2d_inplace(
             out_data,
             method=method,
             axis=axis,

pandas/core/arrays/numpy_.py

@@ -1,6 +1,9 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import (
+    TYPE_CHECKING,
+    Literal,
+)
 
 import numpy as np
 
@@ -32,6 +35,7 @@
     from pandas._typing import (
         AxisInt,
         Dtype,
+        FillnaOptions,
         NpDtype,
         Scalar,
         Self,
@@ -224,12 +228,42 @@ def _values_for_factorize(self) -> tuple[np.ndarray, float | None]:
             fv = np.nan
         return self._ndarray, fv
 
+    def pad_or_backfill(
+        self,
+        *,
+        method: FillnaOptions,
+        axis: int,
+        limit: int | None,
+        limit_area: Literal["inside", "outside"] | None = None,
+        copy: bool = True,
+    ) -> Self:
+        """
+        ffill or bfill
+        """
+        if copy:
+            out_data = self._ndarray.copy()
+        else:
+            out_data = self._ndarray
+
+        meth = missing.clean_fill_method(method)
+        missing.pad_or_backfill_inplace(
+            out_data,
+            method=meth,
+            axis=axis,
+            limit=limit,
+            limit_area=limit_area,
+        )
+
+        if not copy:
+            return self
+        return type(self)._simple_new(out_data, dtype=self.dtype)
+
     def interpolate(
         self,
         *,
         method,
         axis: int,
-        index: Index | None,
+        index: Index,
         limit,
         limit_direction,
         limit_area,
@@ -246,7 +280,8 @@ def interpolate(
         else:
             out_data = self._ndarray.copy()
 
-        missing.interpolate_array_2d(
+        # TODO: assert we have floating dtype?
+        missing.interpolate_2d_inplace(
             out_data,
             method=method,
             axis=axis,

pandas/core/arrays/sparse/array.py

@@ -79,7 +79,7 @@
     check_array_indexer,
     unpack_tuple_and_ellipses,
 )
-from pandas.core.missing import interpolate_2d
+from pandas.core.missing import pad_or_backfill_inplace
 from pandas.core.nanops import check_below_min_count
 
 from pandas.io.formats import printing
@@ -764,11 +764,11 @@ def fillna(
                 stacklevel=find_stack_level(),
             )
             new_values = np.asarray(self)
-            # interpolate_2d modifies new_values inplace
-            # error: Argument "method" to "interpolate_2d" has incompatible type
-            # "Literal['backfill', 'bfill', 'ffill', 'pad']"; expected
+            # pad_or_backfill_inplace modifies new_values inplace
+            # error: Argument "method" to "pad_or_backfill_inplace" has incompatible
+            # type "Literal['backfill', 'bfill', 'ffill', 'pad']"; expected
             # "Literal['pad', 'backfill']"
-            interpolate_2d(
+            pad_or_backfill_inplace(
                 new_values, method=method, limit=limit  # type: ignore[arg-type]
             )
             return type(self)(new_values, fill_value=self.fill_value)

pandas/core/internals/blocks.py

@@ -1381,7 +1381,7 @@ def interpolate(
         inplace: bool = False,
         limit: int | None = None,
         limit_direction: Literal["forward", "backward", "both"] = "forward",
-        limit_area: str | None = None,
+        limit_area: Literal["inside", "outside"] | None = None,
         fill_value: Any | None = None,
         downcast: Literal["infer"] | None = None,
         using_cow: bool = False,
@@ -1439,17 +1439,32 @@ def interpolate(
 
         # Dispatch to the PandasArray method.
         # We know self.array_values is a PandasArray bc EABlock overrides
-        new_values = cast(PandasArray, self.array_values).interpolate(
-            method=method,
-            axis=axis,
-            index=index,
-            limit=limit,
-            limit_direction=limit_direction,
-            limit_area=limit_area,
-            fill_value=fill_value,
-            inplace=arr_inplace,
-            **kwargs,
-        )
+        if m is not None:
+            if fill_value is not None:
+                # similar to validate_fillna_kwargs
+                raise ValueError("Cannot pass both fill_value and method")
+
+            # TODO: warn about ignored kwargs, limit_direction, index...?
+            new_values = cast(PandasArray, self.array_values).pad_or_backfill(
+                method=method,
+                axis=axis,
+                limit=limit,
+                limit_area=limit_area,
+                copy=not arr_inplace,
+            )
+        else:
+            assert index is not None  # for mypy
+            new_values = cast(PandasArray, self.array_values).interpolate(
+                method=method,
+                axis=axis,
+                index=index,
+                limit=limit,
+                limit_direction=limit_direction,
+                limit_area=limit_area,
+                fill_value=fill_value,
+                inplace=arr_inplace,
+                **kwargs,
+            )
         data = new_values._ndarray
 
         nb = self.make_block_same_class(data, refs=refs)

pandas/core/missing.py

@@ -302,60 +302,7 @@ def get_interp_index(method, index: Index) -> Index:
     return index
 
 
-def interpolate_array_2d(
-    data: np.ndarray,
-    method: str = "pad",
-    axis: AxisInt = 0,
-    index: Index | None = None,
-    limit: int | None = None,
-    limit_direction: str = "forward",
-    limit_area: str | None = None,
-    fill_value: Any | None = None,
-    **kwargs,
-) -> None:
-    """
-    Wrapper to dispatch to either interpolate_2d or _interpolate_2d_with_fill.
-
-    Notes
-    -----
-    Alters 'data' in-place.
-    """
-    try:
-        m = clean_fill_method(method)
-    except ValueError:
-        m = None
-
-    if m is not None:
-        if fill_value is not None:
-            # similar to validate_fillna_kwargs
-            raise ValueError("Cannot pass both fill_value and method")
-
-        interpolate_2d(
-            data,
-            method=m,
-            axis=axis,
-            limit=limit,
-            # error: Argument "limit_area" to "interpolate_2d" has incompatible
-            # type "Optional[str]"; expected "Optional[Literal['inside', 'outside']]"
-            limit_area=limit_area,  # type: ignore[arg-type]
-        )
-    else:
-        assert index is not None  # for mypy
-
-        _interpolate_2d_with_fill(
-            data=data,
-            index=index,
-            axis=axis,
-            method=method,
-            limit=limit,
-            limit_direction=limit_direction,
-            limit_area=limit_area,
-            fill_value=fill_value,
-            **kwargs,
-        )
-
-
-def _interpolate_2d_with_fill(
+def interpolate_2d_inplace(
     data: np.ndarray,  # floating dtype
     index: Index,
     axis: AxisInt,
@@ -845,7 +792,7 @@ def _interpolate_with_limit_area(
         if last is None:
             last = len(values)
 
-        interpolate_2d(
+        pad_or_backfill_inplace(
             values,
             method=method,
             limit=limit,
@@ -861,7 +808,7 @@ def _interpolate_with_limit_area(
         values[invalid] = np.nan
 
 
-def interpolate_2d(
+def pad_or_backfill_inplace(
     values: np.ndarray,
     method: Literal["pad", "backfill"] = "pad",
     axis: AxisInt = 0,