From a860d0f58ef2d2b06c4a06370b7a137c74ce7046 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Diridollou?= <loic.diridollou@gmail.com>
Date: Thu, 15 May 2025 20:29:40 -0400
Subject: [PATCH 1/2] GH1214 Improve typehinting for DataFrame.unstack

---
 pandas-stubs/core/frame.pyi |  3 ++-
 tests/test_frame.py         | 46 +++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/pandas-stubs/core/frame.pyi b/pandas-stubs/core/frame.pyi
index 1f8a2648..fb2c1c9b 100644
--- a/pandas-stubs/core/frame.pyi
+++ b/pandas-stubs/core/frame.pyi
@@ -1300,7 +1300,8 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
     def unstack(
         self,
         level: Level = ...,
-        fill_value: int | _str | dict | None = ...,
+        fill_value: Scalar | None = ...,
+        sort: _bool = ...,
     ) -> Self | Series: ...
     def melt(
         self,
diff --git a/tests/test_frame.py b/tests/test_frame.py
index 7d4890ee..3fd76bef 100644
--- a/tests/test_frame.py
+++ b/tests/test_frame.py
@@ -4339,3 +4339,49 @@ def test_df_loc_dict() -> None:
 
     df.iloc[0] = {"X": 0}
     check(assert_type(df, pd.DataFrame), pd.DataFrame)
+
+
+def test_unstack() -> None:
+    """Test different types of argument for `fill_value` in DataFrame.unstack."""
+    df = pd.DataFrame(
+        [
+            ["a", "b", pd.Timestamp(2021, 3, 2)],
+            ["a", "a", pd.Timestamp(2023, 4, 2)],
+            ["b", "b", pd.Timestamp(2024, 3, 2)],
+        ]
+    ).set_index([0, 1])
+
+    check(assert_type(df.unstack(0), pd.DataFrame | pd.Series), pd.DataFrame)
+    check(
+        assert_type(
+            df.unstack(1, fill_value=pd.Timestamp(2023, 4, 5)), pd.DataFrame | pd.Series
+        ),
+        pd.DataFrame,
+    )
+    check(
+        assert_type(df.unstack(1, fill_value=0.0), pd.DataFrame | pd.Series),
+        pd.DataFrame,
+    )
+    check(
+        assert_type(df.unstack(1, fill_value=1), pd.DataFrame | pd.Series), pd.DataFrame
+    )
+    check(
+        assert_type(df.unstack(1, fill_value="string"), pd.DataFrame | pd.Series),
+        pd.DataFrame,
+    )
+    check(
+        assert_type(df.unstack(0, sort=False), pd.DataFrame | pd.Series), pd.DataFrame
+    )
+    check(
+        assert_type(
+            df.unstack(1, fill_value=pd.Timestamp(2023, 4, 5), sort=True),
+            pd.DataFrame | pd.Series,
+        ),
+        pd.DataFrame,
+    )
+    check(
+        assert_type(
+            df.unstack(1, fill_value=0.0, sort=False), pd.DataFrame | pd.Series
+        ),
+        pd.DataFrame,
+    )

From 23adb71f1502d52a5d43b5b9b0fecc62334f0712 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Diridollou?= <loic.diridollou@gmail.com>
Date: Thu, 15 May 2025 20:46:15 -0400
Subject: [PATCH 2/2] GH1214 Fix test

---
 tests/test_frame.py | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/tests/test_frame.py b/tests/test_frame.py
index 3fd76bef..9b666bbc 100644
--- a/tests/test_frame.py
+++ b/tests/test_frame.py
@@ -4350,6 +4350,20 @@ def test_unstack() -> None:
             ["b", "b", pd.Timestamp(2024, 3, 2)],
         ]
     ).set_index([0, 1])
+    df_sr = pd.DataFrame(
+        [
+            ["a", "b", "abc"],
+            ["a", "a", "def"],
+            ["b", "b", "ghi"],
+        ]
+    ).set_index([0, 1])
+    df_flt = pd.DataFrame(
+        [
+            ["a", "b", 1],
+            ["a", "a", 12],
+            ["b", "b", 14],
+        ]
+    ).set_index([0, 1])
 
     check(assert_type(df.unstack(0), pd.DataFrame | pd.Series), pd.DataFrame)
     check(
@@ -4359,14 +4373,15 @@ def test_unstack() -> None:
         pd.DataFrame,
     )
     check(
-        assert_type(df.unstack(1, fill_value=0.0), pd.DataFrame | pd.Series),
+        assert_type(df_flt.unstack(1, fill_value=0.0), pd.DataFrame | pd.Series),
         pd.DataFrame,
     )
     check(
-        assert_type(df.unstack(1, fill_value=1), pd.DataFrame | pd.Series), pd.DataFrame
+        assert_type(df_flt.unstack(1, fill_value=1), pd.DataFrame | pd.Series),
+        pd.DataFrame,
     )
     check(
-        assert_type(df.unstack(1, fill_value="string"), pd.DataFrame | pd.Series),
+        assert_type(df_sr.unstack(1, fill_value="string"), pd.DataFrame | pd.Series),
         pd.DataFrame,
     )
     check(
@@ -4381,7 +4396,7 @@ def test_unstack() -> None:
     )
     check(
         assert_type(
-            df.unstack(1, fill_value=0.0, sort=False), pd.DataFrame | pd.Series
+            df_flt.unstack(1, fill_value=0.0, sort=False), pd.DataFrame | pd.Series
         ),
         pd.DataFrame,
     )