BUG: Fix MutliIndexed unstack failures at tuple names

doc/source/whatsnew/v1.0.0.rst

@@ -1133,6 +1133,7 @@ Reshaping
 - Bug in :func:`merge_asof` merging on a tz-aware ``left_index`` and ``right_on`` a tz-aware column (:issue:`29864`)
 - Improved error message and docstring in :func:`cut` and :func:`qcut` when `labels=True` (:issue:`13318`)
 - Bug in missing `fill_na` parameter to :meth:`DataFrame.unstack` with list of levels (:issue:`30740`)
+- Bug in :func:`unstack` can take tuple names in MultiIndexed data (:issue:`19966`)
 
 Sparse
 ^^^^^^

pandas/core/reshape/reshape.py

@@ -317,6 +317,8 @@ def _unstack_multiple(data, clocs, fill_value=None):
 
     index = data.index
 
+    if clocs in index.names:
+        clocs = [clocs]
     clocs = [index._get_level_number(i) for i in clocs]
 
     rlocs = [i for i in range(index.nlevels) if i not in clocs]

pandas/tests/frame/test_reshape.py

@@ -336,6 +336,80 @@ def test_unstack_fill_frame_categorical(self):
         )
         tm.assert_frame_equal(result, expected)
 
+    def test_unstack_tuplename_in_multiindex(self):
+        # GH 19966
+        idx = pd.MultiIndex.from_product(
+            [["a", "b", "c"], [1, 2, 3]], names=[("A", "a"), ("B", "b")]
+        )
+        df = pd.DataFrame({"d": [1] * 9, "e": [2] * 9}, index=idx)
+        result = df.unstack(("A", "a"))
+
+        expected = pd.DataFrame(
+            [[1, 1, 1, 2, 2, 2], [1, 1, 1, 2, 2, 2], [1, 1, 1, 2, 2, 2]],
+            columns=pd.MultiIndex.from_tuples(
+                [
+                    ("d", "a"),
+                    ("d", "b"),
+                    ("d", "c"),
+                    ("e", "a"),
+                    ("e", "b"),
+                    ("e", "c"),
+                ],
+                names=[None, ("A", "a")],
+            ),
+            index=pd.Index([1, 2, 3], name=("B", "b")),
+        )
+        tm.assert_frame_equal(result, expected)
+
+    @pytest.mark.parametrize(
+        "unstack_idx, expected_values, expected_index, expected_columns",
+        [
+            (
+                ("A", "a"),
+                [[1, 1, 2, 2], [1, 1, 2, 2], [1, 1, 2, 2], [1, 1, 2, 2]],
+                pd.MultiIndex.from_tuples(
+                    [(1, 3), (1, 4), (2, 3), (2, 4)], names=["B", "C"]
+                ),
+                pd.MultiIndex.from_tuples(
+                    [("d", "a"), ("d", "b"), ("e", "a"), ("e", "b")],
+                    names=[None, ("A", "a")],
+                ),
+            ),
+            (
+                (("A", "a"), "B"),
+                [[1, 1, 1, 1, 2, 2, 2, 2], [1, 1, 1, 1, 2, 2, 2, 2]],
+                pd.Index([3, 4], name="C"),
+                pd.MultiIndex.from_tuples(
+                    [
+                        ("d", "a", 1),
+                        ("d", "a", 2),
+                        ("d", "b", 1),
+                        ("d", "b", 2),
+                        ("e", "a", 1),
+                        ("e", "a", 2),
+                        ("e", "b", 1),
+                        ("e", "b", 2),
+                    ],
+                    names=[None, ("A", "a"), "B"],
+                ),
+            ),
+        ],
+    )
+    def test_unstack_mixed_type_name_in_multiindex(
+        self, unstack_idx, expected_values, expected_index, expected_columns
+    ):
+        # GH 19966
+        idx = pd.MultiIndex.from_product(
+            [["a", "b"], [1, 2], [3, 4]], names=[("A", "a"), "B", "C"]
+        )
+        df = pd.DataFrame({"d": [1] * 8, "e": [2] * 8}, index=idx)
+        result = df.unstack(unstack_idx)
+
+        expected = pd.DataFrame(
+            expected_values, columns=expected_columns, index=expected_index,
+        )
+        tm.assert_frame_equal(result, expected)
+
     def test_unstack_preserve_dtypes(self):
         # Checks fix for #11847
         df = pd.DataFrame(

pandas/tests/series/test_reshape.py

@@ -0,0 +1,59 @@
+import pytest
+
+import pandas as pd
+import pandas._testing as tm
+
+
+def test_unstack_tuplename_in_multiindex():
+    # GH 19966
+    idx = pd.MultiIndex.from_product(
+        [["a", "b", "c"], [1, 2, 3]], names=[("A", "a"), ("B", "b")]
+    )
+    ser = pd.Series(1, index=idx)
+    result = ser.unstack(("A", "a"))
+
+    expected = pd.DataFrame(
+        [[1, 1, 1], [1, 1, 1], [1, 1, 1]],
+        columns=pd.MultiIndex.from_tuples(
+            [("a",), ("b",), ("c",)], names=[("A", "a")],
+        ),
+        index=pd.Index([1, 2, 3], name=("B", "b")),
+    )
+    tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "unstack_idx, expected_values, expected_index, expected_columns",
+    [
+        (
+            ("A", "a"),
+            [[1, 1], [1, 1], [1, 1], [1, 1]],
+            pd.MultiIndex.from_tuples(
+                [(1, 3), (1, 4), (2, 3), (2, 4)], names=["B", "C"]
+            ),
+            pd.MultiIndex.from_tuples([("a",), ("b",)], names=[("A", "a")]),
+        ),
+        (
+            (("A", "a"), "B"),
+            [[1, 1, 1, 1], [1, 1, 1, 1]],
+            pd.Index([3, 4], name="C"),
+            pd.MultiIndex.from_tuples(
+                [("a", 1), ("a", 2), ("b", 1), ("b", 2)], names=[("A", "a"), "B"]
+            ),
+        ),
+    ],
+)
+def test_unstack_mixed_type_name_in_multiindex(
+    unstack_idx, expected_values, expected_index, expected_columns
+):
+    # GH 19966
+    idx = pd.MultiIndex.from_product(
+        [["a", "b"], [1, 2], [3, 4]], names=[("A", "a"), "B", "C"]
+    )
+    ser = pd.Series(1, index=idx)
+    result = ser.unstack(unstack_idx)
+
+    expected = pd.DataFrame(
+        expected_values, columns=expected_columns, index=expected_index,
+    )
+    tm.assert_frame_equal(result, expected)