From f74c27c06eaf19c3e5ade20659e689cb54976d74 Mon Sep 17 00:00:00 2001
From: denisrei <39619011+DRiXD@users.noreply.github.com>
Date: Wed, 23 Aug 2023 03:57:19 +0000
Subject: [PATCH 1/3] added test for bug gh#50372

---
 pandas/tests/frame/indexing/test_indexing.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/pandas/tests/frame/indexing/test_indexing.py b/pandas/tests/frame/indexing/test_indexing.py
index 288aa1af746b6..61d30edda94b0 100644
--- a/pandas/tests/frame/indexing/test_indexing.py
+++ b/pandas/tests/frame/indexing/test_indexing.py
@@ -1251,7 +1251,21 @@ def test_type_error_multiindex(self):
 
         result = dg["x", 0]
         tm.assert_series_equal(result, expected)
+    
+    def test_tuple_string_column_names(self):
+        # GH#50372
+        mi = MultiIndex.from_tuples([("a", "aa"), ("a", "ab"), ("b", "ba"), ("b", "bb")])
+        df = DataFrame([range(0, 4), range(1, 5), range(2, 6)], columns=mi)
+        df["single_index"] = 0
 
+        df_flat = df.copy()
+        df_flat.columns = df_flat.columns.to_flat_index()
+        df_flat["new_single_index"] = 0
+
+        df_flat = df_flat[[("a", "aa"), "new_single_index"]]
+
+        assert df_flat.columns.equals(pd.Index([('a', 'aa'), 'new_single_index']))
+       
     def test_getitem_interval_index_partial_indexing(self):
         # GH#36490
         df = DataFrame(

From 15c87fdf0e015756a731cd12be1fa72fce8123bb Mon Sep 17 00:00:00 2001
From: denisrei <39619011+DRiXD@users.noreply.github.com>
Date: Wed, 23 Aug 2023 04:16:54 +0000
Subject: [PATCH 2/3] cleaned code to fit pre-commit

---
 pandas/tests/frame/indexing/test_indexing.py | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/pandas/tests/frame/indexing/test_indexing.py b/pandas/tests/frame/indexing/test_indexing.py
index 61d30edda94b0..08f160639d328 100644
--- a/pandas/tests/frame/indexing/test_indexing.py
+++ b/pandas/tests/frame/indexing/test_indexing.py
@@ -1251,10 +1251,12 @@ def test_type_error_multiindex(self):
 
         result = dg["x", 0]
         tm.assert_series_equal(result, expected)
-    
+
     def test_tuple_string_column_names(self):
         # GH#50372
-        mi = MultiIndex.from_tuples([("a", "aa"), ("a", "ab"), ("b", "ba"), ("b", "bb")])
+        mi = MultiIndex.from_tuples(
+            [("a", "aa"), ("a", "ab"), ("b", "ba"), ("b", "bb")]
+        )
         df = DataFrame([range(0, 4), range(1, 5), range(2, 6)], columns=mi)
         df["single_index"] = 0
 
@@ -1264,8 +1266,8 @@ def test_tuple_string_column_names(self):
 
         df_flat = df_flat[[("a", "aa"), "new_single_index"]]
 
-        assert df_flat.columns.equals(pd.Index([('a', 'aa'), 'new_single_index']))
-       
+        assert df_flat.columns.equals(Index([("a", "aa"), "new_single_index"]))
+
     def test_getitem_interval_index_partial_indexing(self):
         # GH#36490
         df = DataFrame(

From 1bdb01bb3914db5eb9e28d7d14f8869eac324a0d Mon Sep 17 00:00:00 2001
From: denisrei <39619011+DRiXD@users.noreply.github.com>
Date: Wed, 23 Aug 2023 19:07:16 +0000
Subject: [PATCH 3/3] moved test to better fitting location

---
 pandas/tests/frame/indexing/test_indexing.py    | 16 ----------------
 .../tests/indexing/multiindex/test_getitem.py   | 17 +++++++++++++++++
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/pandas/tests/frame/indexing/test_indexing.py b/pandas/tests/frame/indexing/test_indexing.py
index 08f160639d328..288aa1af746b6 100644
--- a/pandas/tests/frame/indexing/test_indexing.py
+++ b/pandas/tests/frame/indexing/test_indexing.py
@@ -1252,22 +1252,6 @@ def test_type_error_multiindex(self):
         result = dg["x", 0]
         tm.assert_series_equal(result, expected)
 
-    def test_tuple_string_column_names(self):
-        # GH#50372
-        mi = MultiIndex.from_tuples(
-            [("a", "aa"), ("a", "ab"), ("b", "ba"), ("b", "bb")]
-        )
-        df = DataFrame([range(0, 4), range(1, 5), range(2, 6)], columns=mi)
-        df["single_index"] = 0
-
-        df_flat = df.copy()
-        df_flat.columns = df_flat.columns.to_flat_index()
-        df_flat["new_single_index"] = 0
-
-        df_flat = df_flat[[("a", "aa"), "new_single_index"]]
-
-        assert df_flat.columns.equals(Index([("a", "aa"), "new_single_index"]))
-
     def test_getitem_interval_index_partial_indexing(self):
         # GH#36490
         df = DataFrame(
diff --git a/pandas/tests/indexing/multiindex/test_getitem.py b/pandas/tests/indexing/multiindex/test_getitem.py
index e2fbc0653695b..9d11827e2923e 100644
--- a/pandas/tests/indexing/multiindex/test_getitem.py
+++ b/pandas/tests/indexing/multiindex/test_getitem.py
@@ -145,6 +145,23 @@ def test_frame_getitem_simple_key_error(
         indexer(df)
 
 
+def test_tuple_string_column_names():
+    # GH#50372
+    mi = MultiIndex.from_tuples([("a", "aa"), ("a", "ab"), ("b", "ba"), ("b", "bb")])
+    df = DataFrame([range(0, 4), range(1, 5), range(2, 6)], columns=mi)
+    df["single_index"] = 0
+
+    df_flat = df.copy()
+    df_flat.columns = df_flat.columns.to_flat_index()
+    df_flat["new_single_index"] = 0
+
+    result = df_flat[[("a", "aa"), "new_single_index"]]
+    expected = DataFrame(
+        [[0, 0], [1, 0], [2, 0]], columns=Index([("a", "aa"), "new_single_index"])
+    )
+    tm.assert_frame_equal(result, expected)
+
+
 def test_frame_getitem_multicolumn_empty_level():
     df = DataFrame({"a": ["1", "2", "3"], "b": ["2", "3", "4"]})
     df.columns = [