BUG: iloc raising for ea and null slice and length one list (pandas-dev#48016)

* BUG: iloc raising for ea and null slice and length one list

* BUG: iloc raising for ea and null slice and length one list

* Parametrize tests

Author: phofl

pandas/core/internals/blocks.py

@@ -1725,6 +1725,9 @@ def _unwrap_setitem_indexer(self, indexer):
                 elif com.is_null_slice(indexer[1]):
                     indexer = indexer[0]
 
+                elif is_list_like(indexer[1]) and indexer[1][0] == 0:
+                    indexer = indexer[0]
+
                 else:
                     raise NotImplementedError(
                         "This should not be reached. Please report a bug at "

pandas/tests/frame/indexing/test_indexing.py

@@ -1363,6 +1363,14 @@ def test_iloc_setitem_string_na(self, val):
         expected = DataFrame({"a": [pd.NA, "b", "c"]}, dtype="string")
         tm.assert_frame_equal(df, expected)
 
+    @pytest.mark.parametrize("func", [list, Series, np.array])
+    def test_iloc_setitem_ea_null_slice_length_one_list(self, func):
+        # GH#48016
+        df = DataFrame({"a": [1, 2, 3]}, dtype="Int64")
+        df.iloc[:, func([0])] = 5
+        expected = DataFrame({"a": [5, 5, 5]}, dtype="Int64")
+        tm.assert_frame_equal(df, expected)
+
 
 class TestDataFrameIndexingUInt64:
     def test_setitem(self, uint64_frame):