Deprecate non-keyword arguments in drop

doc/source/whatsnew/v1.3.0.rst

@@ -647,6 +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 (apart from ``labels``) as positional in :meth:`DataFrame.drop` and :meth:`Series.drop` (:issue:`41485`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/frame.py

@@ -77,6 +77,7 @@
     Appender,
     Substitution,
     deprecate_kwarg,
+    deprecate_nonkeyword_arguments,
     doc,
     rewrite_axis_style_signature,
 )
@@ -4738,6 +4739,7 @@ def reindex(self, *args, **kwargs) -> DataFrame:
         kwargs.pop("labels", None)
         return super().reindex(**kwargs)
 
+    @deprecate_nonkeyword_arguments(version="2.0", allowed_args=["self", "labels"])
     def drop(
         self,
         labels=None,

pandas/core/series.py

@@ -51,6 +51,7 @@
 from pandas.util._decorators import (
     Appender,
     Substitution,
+    deprecate_nonkeyword_arguments,
     doc,
 )
 from pandas.util._validators import (
@@ -4485,6 +4486,7 @@ def set_axis(self, labels, axis: Axis = 0, inplace: bool = False):
     def reindex(self, index=None, **kwargs):
         return super().reindex(index=index, **kwargs)
 
+    @deprecate_nonkeyword_arguments(version="2.0", allowed_args=["self", "labels"])
     def drop(
         self,
         labels=None,

pandas/io/stata.py

@@ -1761,7 +1761,9 @@ def _do_convert_missing(self, data: DataFrame, convert_missing: bool) -> DataFra
         if replacements:
             columns = data.columns
             replacement_df = DataFrame(replacements)
-            replaced = concat([data.drop(replacement_df.columns, 1), replacement_df], 1)
+            replaced = concat(
+                [data.drop(replacement_df.columns, axis=1), replacement_df], 1
+            )
             data = replaced[columns]
         return data
 

pandas/tests/frame/methods/test_drop.py

@@ -89,7 +89,7 @@ def test_drop_names(self):
         with pytest.raises(KeyError, match=msg):
             df.drop(["g"])
         with pytest.raises(KeyError, match=msg):
-            df.drop(["g"], 1)
+            df.drop(["g"], axis=1)
 
         # errors = 'ignore'
         dropped = df.drop(["g"], errors="ignore")
@@ -123,11 +123,11 @@ def test_drop(self):
         with pytest.raises(KeyError, match=r"\[5\] not found in axis"):
             simple.drop(5)
         with pytest.raises(KeyError, match=r"\['C'\] not found in axis"):
-            simple.drop("C", 1)
+            simple.drop("C", axis=1)
         with pytest.raises(KeyError, match=r"\[5\] not found in axis"):
             simple.drop([1, 5])
         with pytest.raises(KeyError, match=r"\['C'\] not found in axis"):
-            simple.drop(["A", "C"], 1)
+            simple.drop(["A", "C"], axis=1)
 
         # errors = 'ignore'
         tm.assert_frame_equal(simple.drop(5, errors="ignore"), simple)
@@ -201,7 +201,7 @@ def test_drop_api_equivalence(self):
         res2 = df.drop(index="a")
         tm.assert_frame_equal(res1, res2)
 
-        res1 = df.drop("d", 1)
+        res1 = df.drop("d", axis=1)
         res2 = df.drop(columns="d")
         tm.assert_frame_equal(res1, res2)
 
@@ -481,3 +481,13 @@ def test_drop_with_duplicate_columns2(self):
         df2 = df.take([2, 0, 1, 2, 1], axis=1)
         result = df2.drop("C", axis=1)
         tm.assert_frame_equal(result, expected)
+
+    def test_drop_pos_args_deprecation(self):
+        # https://github.com/pandas-dev/pandas/issues/41485
+        df = DataFrame({"a": [1, 2, 3]})
+        msg = (
+            r"Starting with Pandas version 2\.0 all arguments of drop except for the "
+            r"arguments 'self' and 'labels' will be keyword-only"
+        )
+        with tm.assert_produces_warning(FutureWarning, match=msg):
+            df.drop("a", 1)

pandas/tests/groupby/transform/test_transform.py

@@ -883,7 +883,7 @@ def test_pad_stable_sorting(fill_method):
         y = y[::-1]
 
     df = DataFrame({"x": x, "y": y})
-    expected = df.drop("x", 1)
+    expected = df.drop("x", axis=1)
 
     result = getattr(df.groupby("x"), fill_method)()
 

pandas/tests/series/methods/test_drop.py

@@ -84,3 +84,14 @@ def test_drop_non_empty_list(data, index, drop_labels):
     ser = Series(data=data, index=index, dtype=dtype)
     with pytest.raises(KeyError, match="not found in axis"):
         ser.drop(drop_labels)
+
+
+def test_drop_pos_args_deprecation():
+    # https://github.com/pandas-dev/pandas/issues/41485
+    ser = Series([1, 2, 3])
+    msg = (
+        r"Starting with Pandas version 2\.0 all arguments of drop except for the "
+        r"arguments 'self' and 'labels' will be keyword-only"
+    )
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        ser.drop(1, 0)