ENH: Deprecate non-keyword arguments for drop_duplicates.

Author: jmholzer

pandas/core/frame.py

@@ -6005,7 +6005,7 @@ def dropna(
         else:
             return result
 
-    @deprecate_nonkeyword_arguments(version="2.0", allowed_args=["self"])
+    @deprecate_nonkeyword_arguments(version="2.0", allowed_args=["self", "subset"])
     def drop_duplicates(
         self,
         subset: Hashable | Sequence[Hashable] | None = None,

pandas/tests/frame/methods/test_drop_duplicates.py

@@ -474,11 +474,11 @@ def test_drop_duplicates_non_boolean_ignore_index(arg):
 
 
 def test_drop_duplicates_pos_args_deprecation():
-    # test deprecation warning message for positional arguments GH#41485
+    # GH#41485
     df = DataFrame({"a": [1, 1, 2], "b": [1, 1, 3], "c": [1, 1, 3]})
     msg = (
-        r"Starting with Pandas version 2\.0 all arguments of drop_duplicates except for "
-        r"the argument 'self' will be keyword-only"
+        r"Starting with Pandas version 2\.0 all arguments of drop_duplicates "
+        r"except for the argument 'self' will be keyword-only"
     )
     with tm.assert_produces_warning(FutureWarning, match=msg):
         df.drop_duplicates(["b", "c"])

pandas/tests/series/methods/test_drop_duplicates.py

@@ -226,11 +226,11 @@ def test_drop_duplicates_categorical_bool(self, ordered):
 
 
 def test_drop_duplicates_pos_args_deprecation():
-    # test deprecation warning message for positional arguments GH#41485
-    s = Series(['a', 'b', 'c', 'b'])
+    # GH#41485
+    s = Series(["a", "b", "c", "b"])
     msg = (
-        r"Starting with Pandas version 2\.0 all arguments of drop_duplicates except for "
-        r"the argument 'self' will be keyword-only"
+        r"Starting with Pandas version 2\.0 all arguments of drop_duplicates "
+        r"except for the argument 'self' will be keyword-only"
     )
     with tm.assert_produces_warning(FutureWarning, match=msg):
         s.drop_duplicates("last")