Deprecate non-keyword arguments in drop (#41486)

Author: MarcoGorelli

doc/source/whatsnew/v1.3.0.rst

@@ -693,6 +693,7 @@ Deprecations
 - Deprecated passing arguments as positional in :meth:`DataFrame.reset_index` (other than ``"level"``) and :meth:`Series.reset_index` (:issue:`41485`)
 - Deprecated construction of :class:`Series` or :class:`DataFrame` with ``DatetimeTZDtype`` data and ``datetime64[ns]`` dtype.  Use ``Series(data).dt.tz_localize(None)`` instead (:issue:`41555`,:issue:`33401`)
 - Deprecated passing arguments as positional in :meth:`DataFrame.where` and :meth:`Series.where` (other than ``"cond"`` and ``"other"``) (:issue:`41485`)
+- Deprecated passing arguments as positional in :meth:`DataFrame.drop` (other than ``"labels"``) and :meth:`Series.drop` (:issue:`41485`)
 -
 
 .. _whatsnew_130.deprecations.nuisance_columns:

pandas/core/frame.py

@@ -4766,6 +4766,7 @@ def reindex(self, *args, **kwargs) -> DataFrame:
         kwargs.pop("labels", None)
         return super().reindex(**kwargs)
 
+    @deprecate_nonkeyword_arguments(version=None, allowed_args=["self", "labels"])
     def drop(
         self,
         labels=None,

pandas/core/series.py

@@ -4522,6 +4522,7 @@ 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=None, 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)
 
@@ -482,6 +482,18 @@ def test_drop_with_duplicate_columns2(self):
         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"In a future version of pandas all arguments of DataFrame\.drop "
+            r"except for the argument 'labels' will be keyword-only"
+        )
+        with tm.assert_produces_warning(FutureWarning, match=msg):
+            result = df.drop("a", 1)
+        expected = DataFrame(index=[0, 1, 2])
+        tm.assert_frame_equal(result, expected)
+
     def test_drop_inplace_no_leftover_column_reference(self):
         # GH 13934
         df = DataFrame({"a": [1, 2, 3]})

pandas/tests/groupby/transform/test_transform.py

@@ -901,7 +901,7 @@ 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 +84,16 @@ 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"In a future version of pandas all arguments of Series\.drop "
+        r"except for the argument 'labels' will be keyword-only"
+    )
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        result = ser.drop(1, 0)
+    expected = Series([1, 3], index=[0, 2])
+    tm.assert_series_equal(result, expected)