From 030e792b27313a16fed13362ab8953980b75fc45 Mon Sep 17 00:00:00 2001
From: Brock <jbrockmendel@gmail.com>
Date: Sat, 25 Oct 2025 14:27:38 -0700
Subject: [PATCH] DEPR: inplace keyword in interpolate.resample

---
 doc/source/whatsnew/v3.0.0.rst     |  1 +
 pandas/core/resample.py            | 23 ++++++++++++++++++-----
 pandas/tests/resample/test_base.py | 18 ++++++++++++++++++
 3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst
index 75b4c5c0fe14d..82019c4917fac 100644
--- a/doc/source/whatsnew/v3.0.0.rst
+++ b/doc/source/whatsnew/v3.0.0.rst
@@ -737,6 +737,7 @@ Other Deprecations
 - Deprecated backward-compatibility behavior for :meth:`DataFrame.select_dtypes` matching "str" dtype when ``np.object_`` is specified (:issue:`61916`)
 - Deprecated option "future.no_silent_downcasting", as it is no longer used. In a future version accessing this option will raise (:issue:`59502`)
 - Deprecated slicing on a :class:`Series` or :class:`DataFrame` with a :class:`DatetimeIndex` using a ``datetime.date`` object, explicitly cast to :class:`Timestamp` instead (:issue:`35830`)
+- Deprecated the 'inplace' keyword from :meth:`Resampler.interpolate`, as passing ``True`` raises ``AttributeError`` (:issue:`58690`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_300.prior_deprecations:
diff --git a/pandas/core/resample.py b/pandas/core/resample.py
index 3a4ce952ffdcf..4e638be8e1052 100644
--- a/pandas/core/resample.py
+++ b/pandas/core/resample.py
@@ -26,7 +26,10 @@
     to_offset,
 )
 from pandas._typing import NDFrameT
-from pandas.errors import AbstractMethodError
+from pandas.errors import (
+    AbstractMethodError,
+    Pandas4Warning,
+)
 from pandas.util._exceptions import find_stack_level
 
 from pandas.core.dtypes.dtypes import (
@@ -847,7 +850,6 @@ def interpolate(
         *,
         axis: Axis = 0,
         limit: int | None = None,
-        inplace: bool = False,
         limit_direction: Literal["forward", "backward", "both"] = "forward",
         limit_area=None,
         downcast=lib.no_default,
@@ -893,8 +895,6 @@ def interpolate(
         limit : int, optional
             Maximum number of consecutive NaNs to fill. Must be greater than
             0.
-        inplace : bool, default False
-            Update the data in place if possible.
         limit_direction : {{'forward', 'backward', 'both'}}, Optional
             Consecutive NaNs will be filled in this direction.
 
@@ -993,6 +993,19 @@ def interpolate(
         Note that the series correctly decreases between two anchors
         ``07:00:00`` and ``07:00:02``.
         """
+        if "inplace" in kwargs:
+            # GH#58690
+            warnings.warn(
+                f"The 'inplace' keyword in {type(self).__name__}.interpolate "
+                "is deprecated and will be removed in a future version. "
+                "resample(...).interpolate is never inplace.",
+                Pandas4Warning,
+                stacklevel=find_stack_level(),
+            )
+            inplace = kwargs.pop("inplace")
+            if inplace:
+                raise ValueError("Cannot interpolate inplace on a resampled object.")
+
         assert downcast is lib.no_default  # just checking coverage
         result = self._upsample("asfreq")
 
@@ -1027,7 +1040,7 @@ def interpolate(
             method=method,
             axis=axis,
             limit=limit,
-            inplace=inplace,
+            inplace=False,
             limit_direction=limit_direction,
             limit_area=limit_area,
             downcast=downcast,
diff --git a/pandas/tests/resample/test_base.py b/pandas/tests/resample/test_base.py
index 12128be7c2d30..6bfad10b5c32d 100644
--- a/pandas/tests/resample/test_base.py
+++ b/pandas/tests/resample/test_base.py
@@ -3,6 +3,8 @@
 import numpy as np
 import pytest
 
+from pandas.errors import Pandas4Warning
+
 from pandas.core.dtypes.common import is_extension_array_dtype
 
 import pandas as pd
@@ -109,6 +111,22 @@ def test_resample_interpolate(index):
     tm.assert_frame_equal(result, expected)
 
 
+def test_resample_interpolate_inplace_deprecated():
+    # GH#58690
+    dti = date_range(datetime(2005, 1, 1), datetime(2005, 1, 10), freq="D")
+
+    df = DataFrame(range(len(dti)), index=dti)
+    rs = df.resample("1min")
+    msg = "The 'inplace' keyword in DatetimeIndexResampler.interpolate"
+    with tm.assert_produces_warning(Pandas4Warning, match=msg):
+        rs.interpolate(inplace=False)
+
+    msg2 = "Cannot interpolate inplace on a resampled object"
+    with pytest.raises(ValueError, match=msg2):
+        with tm.assert_produces_warning(Pandas4Warning, match=msg):
+            rs.interpolate(inplace=True)
+
+
 def test_resample_interpolate_regular_sampling_off_grid(
     all_1d_no_arg_interpolation_methods,
 ):