ENH: EA.interpolate (#53659)

* ENH: EA.interpolate * update code check * update docstring to appease code check * inplace->copy * whatsnew

Author: jbrockmendel

ci/code_checks.sh

@@ -231,6 +231,7 @@ if [[ -z "$CHECK" || "$CHECK" == "docstrings" ]]; then
  pandas.api.extensions.ExtensionArray.factorize \
  pandas.api.extensions.ExtensionArray.fillna \
  pandas.api.extensions.ExtensionArray.insert \
+ pandas.api.extensions.ExtensionArray.interpolate \
  pandas.api.extensions.ExtensionArray.isin \
  pandas.api.extensions.ExtensionArray.isna \
  pandas.api.extensions.ExtensionArray.ravel \

doc/source/reference/extensions.rst

@@ -51,6 +51,7 @@ objects.
  api.extensions.ExtensionArray.factorize
  api.extensions.ExtensionArray.fillna
  api.extensions.ExtensionArray.insert
+ api.extensions.ExtensionArray.interpolate
  api.extensions.ExtensionArray.isin
  api.extensions.ExtensionArray.isna
  api.extensions.ExtensionArray.ravel

doc/source/whatsnew/v2.1.0.rst

@@ -110,13 +110,15 @@ Other enhancements
 - :meth:`Series.str.join` now supports ``ArrowDtype(pa.string())`` (:issue:`53646`)
 - :meth:`SeriesGroupby.agg` and :meth:`DataFrameGroupby.agg` now support passing in multiple functions for ``engine="numba"`` (:issue:`53486`)
 - :meth:`SeriesGroupby.transform` and :meth:`DataFrameGroupby.transform` now support passing in a string as the function for ``engine="numba"`` (:issue:`53579`)
+- Added :meth:`ExtensionArray.interpolate` used by :meth:`Series.interpolate` and :meth:`DataFrame.interpolate` (:issue:`53659`)
 - Added ``engine_kwargs`` parameter to :meth:`DataFrame.to_excel` (:issue:`53220`)
 - Added a new parameter ``by_row`` to :meth:`Series.apply`. When set to ``False`` the supplied callables will always operate on the whole Series (:issue:`53400`).
 - Groupby aggregations (such as :meth:`DataFrameGroupby.sum`) now can preserve the dtype of the input instead of casting to ``float64`` (:issue:`44952`)
 - Improved error message when :meth:`DataFrameGroupBy.agg` failed (:issue:`52930`)
 - Many read/to_* functions, such as :meth:`DataFrame.to_pickle` and :func:`read_csv`, support forwarding compression arguments to lzma.LZMAFile (:issue:`52979`)
 - Performance improvement in :func:`concat` with homogeneous ``np.float64`` or ``np.float32`` dtypes (:issue:`52685`)
 - Performance improvement in :meth:`DataFrame.filter` when ``items`` is given (:issue:`52941`)
+-
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_210.notable_bug_fixes:

pandas/_typing.py

@@ -307,6 +307,26 @@ def closed(self) -> bool:
 
 # Arguments for fillna()
 FillnaOptions = Literal["backfill", "bfill", "ffill", "pad"]
+InterpolateOptions = Literal[
+ "linear",
+ "time",
+ "index",
+ "values",
+ "nearest",
+ "zero",
+ "slinear",
+ "quadratic",
+ "cubic",
+ "barycentric",
+ "polynomial",
+ "krogh",
+ "piecewise_polynomial",
+ "spline",
+ "pchip",
+ "akima",
+ "cubicspline",
+ "from_derivatives",
+]
 
 # internals
 Manager = Union[

pandas/core/arrays/base.py

@@ -78,6 +78,7 @@
  AxisInt,
  Dtype,
  FillnaOptions,
+ InterpolateOptions,
  NumpySorter,
  NumpyValueArrayLike,
  PositionalIndexer,
@@ -90,6 +91,8 @@
  npt,
  )
 
+ from pandas import Index
+
 _extension_array_shared_docs: dict[str, str] = {}
 
 
@@ -118,6 +121,7 @@ class ExtensionArray:
  fillna
  equals
  insert
+ interpolate
  isin
  isna
  ravel
@@ -155,6 +159,7 @@ class ExtensionArray:
  * take
  * copy
  * _concat_same_type
+ * interpolate
 
  A default repr displaying the type, (truncated) data, length,
  and dtype is provided. It can be customized or replaced by
@@ -753,6 +758,27 @@ def argmax(self, skipna: bool = True) -> int:
  raise NotImplementedError
  return nargminmax(self, "argmax")
 
+ def interpolate(
+ self,
+ *,
+ method: InterpolateOptions,
+ axis: int,
+ index: Index,
+ limit,
+ limit_direction,
+ limit_area,
+ fill_value,
+ copy: bool,
+ **kwargs,
+ ) -> Self:
+ """
+ See DataFrame.interpolate.__doc__.
+ """
+ # NB: we return type(self) even if copy=False
+ raise NotImplementedError(
+ f"{type(self).__name__} does not implement interpolate"
+ )
+
  def fillna(
  self,
  value: object | ArrayLike | None = None,

pandas/core/arrays/datetimelike.py

@@ -58,6 +58,7 @@
  Dtype,
  DtypeObj,
  F,
+ InterpolateOptions,
  NpDtype,
  PositionalIndexer2D,
  PositionalIndexerTuple,
@@ -2233,23 +2234,23 @@ def copy(self, order: str = "C") -> Self:
  def interpolate(
  self,
  *,
- method,
+ method: InterpolateOptions,
  axis: int,
  index: Index,
  limit,
  limit_direction,
  limit_area,
- inplace: bool,
+ copy: bool,
  **kwargs,
  ) -> Self:
  """
  See NDFrame.interpolate.__doc__.
  """
- # NB: we return type(self) even if inplace=True
+ # NB: we return type(self) even if copy=False
  if method != "linear":
  raise NotImplementedError
 
- if inplace:
+ if not copy:
  out_data = self._ndarray
  else:
  out_data = self._ndarray.copy()
@@ -2264,7 +2265,7 @@ def interpolate(
  limit_area=limit_area,
  **kwargs,
  )
- if inplace:
+ if not copy:
  return self
  return type(self)._simple_new(out_data, dtype=self.dtype)
 

pandas/core/arrays/numpy_.py

@@ -36,6 +36,7 @@
  AxisInt,
  Dtype,
  FillnaOptions,
+ InterpolateOptions,
  NpDtype,
  Scalar,
  Self,
@@ -261,20 +262,20 @@ def pad_or_backfill(
  def interpolate(
  self,
  *,
- method,
+ method: InterpolateOptions,
  axis: int,
  index: Index,
  limit,
  limit_direction,
  limit_area,
- inplace: bool,
+ copy: bool,
  **kwargs,
  ) -> Self:
  """
  See NDFrame.interpolate.__doc__.
  """
- # NB: we return type(self) even if inplace=True
- if inplace:
+ # NB: we return type(self) even if copy=False
+ if not copy:
  out_data = self._ndarray
  else:
  out_data = self._ndarray.copy()
@@ -290,7 +291,7 @@ def interpolate(
  limit_area=limit_area,
  **kwargs,
  )
- if inplace:
+ if not copy:
  return self
  return type(self)._simple_new(out_data, dtype=self.dtype)
 

pandas/core/generic.py

@@ -62,6 +62,7 @@
  IgnoreRaise,
  IndexKeyFunc,
  IndexLabel,
+ InterpolateOptions,
  IntervalClosedType,
  JSONSerializable,
  Level,
@@ -7753,27 +7754,7 @@ def replace(
  @final
  def interpolate(
  self,
- method: Literal[
- "linear",
- "time",
- "index",
- "values",
- "pad",
- "nearest",
- "zero",
- "slinear",
- "quadratic",
- "cubic",
- "barycentric",
- "polynomial",
- "krogh",
- "piecewise_polynomial",
- "spline",
- "pchip",
- "akima",
- "cubicspline",
- "from_derivatives",
- ] = "linear",
+ method: InterpolateOptions = "linear",
  *,
  axis: Axis = 0,
  limit: int | None = None,