allow method to be positional

Author: MarcoGorelli

doc/source/whatsnew/v1.3.0.rst

@@ -647,7 +647,7 @@ Deprecations
 - Deprecated setting :attr:`Categorical._codes`, create a new :class:`Categorical` with the desired codes instead (:issue:`40606`)
 - Deprecated behavior of :meth:`DatetimeIndex.union` with mixed timezones; in a future version both will be cast to UTC instead of object dtype (:issue:`39328`)
 - Deprecated using ``usecols`` with out of bounds indices for ``read_csv`` with ``engine="c"`` (:issue:`25623`)
-- Deprecated passing arguments as positional in :meth:`DataFrame.interpolate` and :meth:`Series.interpolate` (:issue:`41485`)
+- Deprecated passing arguments as positional (except for ``"method"``) in :meth:`DataFrame.interpolate` and :meth:`Series.interpolate` (:issue:`41485`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/generic.py

@@ -6697,7 +6697,7 @@ def replace(
         else:
             return result.__finalize__(self, method="replace")
 
-    @deprecate_nonkeyword_arguments(version="2.0", allowed_args=["self"])
+    @deprecate_nonkeyword_arguments(version="2.0", allowed_args=["self", "method"])
     @final
     def interpolate(
         self: FrameOrSeries,

pandas/tests/frame/methods/test_interpolate.py

@@ -348,7 +348,7 @@ def test_interpolate_pos_args_deprecation(self):
         df = DataFrame({"a": [1, 2, 3]})
         msg = (
             r"Starting with Pandas version 2\.0 all arguments of interpolate except "
-            r"for the argument 'self' will be keyword-only"
+            r"for the arguments 'self' and 'method' will be keyword-only"
         )
         with tm.assert_produces_warning(FutureWarning, match=msg):
-            df.interpolate(0)
+            df.interpolate("pad", 0)

pandas/tests/series/methods/test_interpolate.py

@@ -817,7 +817,7 @@ def test_interpolate_pos_args_deprecation(self):
         ser = Series([1, 2, 3])
         msg = (
             r"Starting with Pandas version 2\.0 all arguments of interpolate except "
-            r"for the argument 'self' will be keyword-only"
+            r"for the arguments 'self' and 'method' will be keyword-only"
         )
         with tm.assert_produces_warning(FutureWarning, match=msg):
-            ser.interpolate(0)
+            ser.interpolate("pad", 0)