From f607a10ac69cc5d53a40c3f68599c67ea4f342b9 Mon Sep 17 00:00:00 2001
From: 01-vyom <angerstick3@gmail.com>
Date: Fri, 21 May 2021 01:22:54 +0530
Subject: [PATCH 1/2] ENH: Deprecate non-keyword arguments for
 MultiIndex.set_levels

---
 doc/source/whatsnew/v1.3.0.rst             |  1 +
 pandas/core/indexes/multi.py               |  2 ++
 pandas/tests/indexes/multi/test_get_set.py | 29 +++++++++++++++++++++-
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v1.3.0.rst b/doc/source/whatsnew/v1.3.0.rst
index 1eb22436204a8..2b81ae80f26b9 100644
--- a/doc/source/whatsnew/v1.3.0.rst
+++ b/doc/source/whatsnew/v1.3.0.rst
@@ -649,6 +649,7 @@ Deprecations
 - 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 (except for ``"method"``) in :meth:`DataFrame.interpolate` and :meth:`Series.interpolate` (:issue:`41485`)
+- Deprecated passing arguments as positional (except for ``"levels"``) in :meth:`MultiIndex.set_levels` (:issue:`41485`)
 
 .. ---------------------------------------------------------------------------
 
diff --git a/pandas/core/indexes/multi.py b/pandas/core/indexes/multi.py
index 1a3719233a1da..cc6c3c3fdb0f9 100644
--- a/pandas/core/indexes/multi.py
+++ b/pandas/core/indexes/multi.py
@@ -41,6 +41,7 @@
 from pandas.util._decorators import (
     Appender,
     cache_readonly,
+    deprecate_nonkeyword_arguments,
     doc,
 )
 
@@ -807,6 +808,7 @@ def _set_levels(
 
         self._reset_cache()
 
+    @deprecate_nonkeyword_arguments(version=None, allowed_args=["self", "levels"])
     def set_levels(
         self, levels, level=None, inplace=None, verify_integrity: bool = True
     ):
diff --git a/pandas/tests/indexes/multi/test_get_set.py b/pandas/tests/indexes/multi/test_get_set.py
index 0c561395788ad..98fe0fada0bb6 100644
--- a/pandas/tests/indexes/multi/test_get_set.py
+++ b/pandas/tests/indexes/multi/test_get_set.py
@@ -351,7 +351,7 @@ def test_set_levels_categorical(ordered):
     index = MultiIndex.from_arrays([list("xyzx"), [0, 1, 2, 3]])
 
     cidx = CategoricalIndex(list("bac"), ordered=ordered)
-    result = index.set_levels(cidx, 0)
+    result = index.set_levels(cidx, level=0)
     expected = MultiIndex(levels=[cidx, [0, 1, 2, 3]], codes=index.codes)
     tm.assert_index_equal(result, expected)
 
@@ -405,3 +405,30 @@ def test_set_levels_inplace_deprecated(idx, inplace):
 
     with tm.assert_produces_warning(FutureWarning):
         idx.set_levels(levels=new_level, level=1, inplace=inplace)
+
+
+def test_set_levels_pos_args_deprecation():
+    # https://github.com/pandas-dev/pandas/issues/41485
+    idx = MultiIndex.from_tuples(
+        [
+            (1, "one"),
+            (2, "one"),
+            (3, "one"),
+        ],
+        names=["foo", "bar"],
+    )
+    msg = (
+        r"In a future version of pandas all arguments of MultiIndex.set_levels except "
+        r"for the arguments 'levels' will be keyword-only"
+    )
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        result = idx.set_levels(["a", "b", "c"], 0)
+    expected = MultiIndex.from_tuples(
+        [
+            ("a", "one"),
+            ("b", "one"),
+            ("c", "one"),
+        ],
+        names=["foo", "bar"],
+    )
+    tm.assert_index_equal(result, expected)

From a13c8acb0774d857f7dfdaf4d77d0008a466a243 Mon Sep 17 00:00:00 2001
From: 01-vyom <angerstick3@gmail.com>
Date: Sun, 23 May 2021 16:03:58 +0530
Subject: [PATCH 2/2] BUG: Changed stack levels and test message string

---
 pandas/core/indexes/multi.py               | 2 +-
 pandas/tests/indexes/multi/test_get_set.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/core/indexes/multi.py b/pandas/core/indexes/multi.py
index cc6c3c3fdb0f9..e39a6cd672bde 100644
--- a/pandas/core/indexes/multi.py
+++ b/pandas/core/indexes/multi.py
@@ -900,7 +900,7 @@ def set_levels(
             warnings.warn(
                 "inplace is deprecated and will be removed in a future version.",
                 FutureWarning,
-                stacklevel=2,
+                stacklevel=3,
             )
         else:
             inplace = False
diff --git a/pandas/tests/indexes/multi/test_get_set.py b/pandas/tests/indexes/multi/test_get_set.py
index 98fe0fada0bb6..9657e74c363b9 100644
--- a/pandas/tests/indexes/multi/test_get_set.py
+++ b/pandas/tests/indexes/multi/test_get_set.py
@@ -419,7 +419,7 @@ def test_set_levels_pos_args_deprecation():
     )
     msg = (
         r"In a future version of pandas all arguments of MultiIndex.set_levels except "
-        r"for the arguments 'levels' will be keyword-only"
+        r"for the argument 'levels' will be keyword-only"
     )
     with tm.assert_produces_warning(FutureWarning, match=msg):
         result = idx.set_levels(["a", "b", "c"], 0)