BUG: Fix bug in reindexing of period columns after unstack (#61114)

Author: snitish

doc/source/whatsnew/v3.0.0.rst

@@ -703,6 +703,7 @@ Indexing
 - Bug in :meth:`Index.get_indexer` and similar methods when ``NaN`` is located at or after position 128 (:issue:`58924`)
 - Bug in :meth:`MultiIndex.insert` when a new value inserted to a datetime-like level gets cast to ``NaT`` and fails indexing (:issue:`60388`)
 - Bug in printing :attr:`Index.names` and :attr:`MultiIndex.levels` would not escape single quotes (:issue:`60190`)
+- Bug in reindexing of :class:`DataFrame` with :class:`PeriodDtype` columns in case of consolidated block (:issue:`60980`, :issue:`60273`)
 
 Missing
 ^^^^^^^

pandas/core/internals/blocks.py

@@ -155,12 +155,9 @@ class Block(PandasObject, libinternals.Block):
     def _validate_ndim(self) -> bool:
         """
         We validate dimension for blocks that can hold 2D values, which for now
-        means numpy dtypes or DatetimeTZDtype.
+        means numpy dtypes or EA dtypes like DatetimeTZDtype and PeriodDtype.
         """
-        dtype = self.dtype
-        return not isinstance(dtype, ExtensionDtype) or isinstance(
-            dtype, DatetimeTZDtype
-        )
+        return not is_1d_only_ea_dtype(self.dtype)
 
     @final
     @cache_readonly

pandas/tests/indexing/test_indexing.py

@@ -763,6 +763,27 @@ def test_partial_boolean_frame_indexing(self):
         )
         tm.assert_frame_equal(result, expected)
 
+    def test_period_column_slicing(self):
+        # GH#60273 The transpose operation creates a single 5x1 block of PeriodDtype
+        # Make sure it is reindexed correctly
+        df = DataFrame(
+            pd.period_range("2021-01-01", periods=5, freq="D"),
+            columns=["A"],
+        ).T
+        result = df[[0, 1, 2]]
+        expected = DataFrame(
+            [
+                [
+                    pd.Period("2021-01-01", freq="D"),
+                    pd.Period("2021-01-02", freq="D"),
+                    pd.Period("2021-01-03", freq="D"),
+                ]
+            ],
+            index=["A"],
+            columns=[0, 1, 2],
+        )
+        tm.assert_frame_equal(result, expected)
+
     def test_no_reference_cycle(self):
         df = DataFrame({"a": [0, 1], "b": [2, 3]})
         for name in ("loc", "iloc", "at", "iat"):

pandas/tests/internals/test_internals.py

@@ -1320,6 +1320,16 @@ def test_period_can_hold_element(self, element):
         with pytest.raises(TypeError, match="Invalid value"):
             self.check_series_setitem(elem, pi, False)
 
+    def test_period_reindex_axis(self):
+        # GH#60273 Test reindexing of block with PeriodDtype
+        pi = period_range("2020", periods=5, freq="Y")
+        blk = new_block(pi._data.reshape(5, 1), BlockPlacement(slice(5)), ndim=2)
+        mgr = BlockManager(blocks=(blk,), axes=[Index(np.arange(5)), Index(["a"])])
+        reindexed = mgr.reindex_axis(Index([0, 2, 4]), axis=0)
+        result = DataFrame._from_mgr(reindexed, axes=reindexed.axes)
+        expected = DataFrame([[pi[0], pi[2], pi[4]]], columns=[0, 2, 4], index=["a"])
+        tm.assert_frame_equal(result, expected)
+
     def check_can_hold_element(self, obj, elem, inplace: bool):
         blk = obj._mgr.blocks[0]
         if inplace: