ENH: Deprecate non-keyword arguments for Resampler.interpolate

doc/source/whatsnew/v1.3.0.rst

@@ -686,6 +686,7 @@ Deprecations
 - Deprecated passing arguments as positional (except for ``"codes"``) in :meth:`MultiIndex.codes` (:issue:`41485`)
 - Deprecated passing arguments as positional in :meth:`Index.set_names` and :meth:`MultiIndex.set_names` (except for ``names``) (:issue:`41485`)
 - Deprecated passing arguments (apart from ``cond`` and ``other``) as positional in :meth:`DataFrame.mask` and :meth:`Series.mask` (:issue:`41485`)
+- Deprecated passing arguments as positional in :meth:`Resampler.interpolate` (other than ``"method"``) (:issue:`41485`)
 - Deprecated passing arguments as positional in :meth:`DataFrame.clip` and :meth:`Series.clip` (other than ``"upper"`` and ``"lower"``) (:issue:`41485`)
 - Deprecated special treatment of lists with first element a Categorical in the :class:`DataFrame` constructor; pass as ``pd.DataFrame({col: categorical, ...})`` instead (:issue:`38845`)
 - Deprecated behavior of :class:`DataFrame` constructor when a ``dtype`` is passed and the data cannot be cast to that dtype. In a future version, this will raise instead of being silently ignored (:issue:`24435`)

pandas/core/resample.py

@@ -34,6 +34,7 @@
 from pandas.util._decorators import (
     Appender,
     Substitution,
+    deprecate_nonkeyword_arguments,
     doc,
 )
 
@@ -832,6 +833,7 @@ def fillna(self, method, limit=None):
         """
         return self._upsample(method, limit=limit)
 
+    @deprecate_nonkeyword_arguments(version=None, allowed_args=["self", "method"])
     @doc(NDFrame.interpolate, **_shared_docs_kwargs)
     def interpolate(
         self,

pandas/tests/resample/test_deprecated.py

@@ -278,3 +278,30 @@ def test_resample_base_with_timedeltaindex():
 
     tm.assert_index_equal(without_base.index, exp_without_base)
     tm.assert_index_equal(with_base.index, exp_with_base)
+
+
+def test_interpolate_posargs_deprecation():
+    # GH 41485
+    idx = pd.to_datetime(["1992-08-27 07:46:48", "1992-08-27 07:46:59"])
+    s = Series([1, 4], index=idx)
+
+    msg = (
+        r"In a future version of pandas all arguments of Resampler\.interpolate "
+        r"except for the argument 'method' will be keyword-only"
+    )
+
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        result = s.resample("3s").interpolate("linear", 0)
+
+    idx = pd.to_datetime(
+        [
+            "1992-08-27 07:46:48",
+            "1992-08-27 07:46:51",
+            "1992-08-27 07:46:54",
+            "1992-08-27 07:46:57",
+        ]
+    )
+    expected = Series([1.0, 1.0, 1.0, 1.0], index=idx)
+
+    expected.index._data.freq = "3s"
+    tm.assert_series_equal(result, expected)