BUG: Fix _validate_key to handle ExtensionArray correctly GH#61311

Author: skonda29

pandas/core/indexing.py

@@ -1609,9 +1609,16 @@ def _validate_key(self, key, axis: AxisInt) -> None:
             if not is_numeric_dtype(arr.dtype):
                 raise IndexError(f".iloc requires numeric indexers, got {arr}")
 
-            # check that the key does not exceed the maximum size of the index
-            if len(arr) and (arr.max() >= len_axis or arr.min() < -len_axis):
-                raise IndexError("positional indexers are out-of-bounds")
+            if len(arr):
+                # convert to numpy array for min/max with ExtensionArrays
+                if hasattr(arr, "to_numpy"):
+                    np_arr = arr.to_numpy()
+                else:
+                    np_arr = np.asarray(arr)
+
+                # check that the key does not exceed the maximum size
+                if np.max(np_arr) >= len_axis or np.min(np_arr) < -len_axis:
+                    raise IndexError("positional indexers are out-of-bounds")
         else:
             raise ValueError(f"Can only index by location with a [{self._valid_types}]")
 

pandas/tests/indexing/test_iloc.py

@@ -1478,3 +1478,14 @@ def test_iloc_nullable_int64_size_1_nan(self):
         result = DataFrame({"a": ["test"], "b": [np.nan]})
         with pytest.raises(TypeError, match="Invalid value"):
             result.loc[:, "b"] = result.loc[:, "b"].astype("Int64")
+
+    def test_iloc_arrow_extension_array(self):
+        # GH#61311
+        pytest.importorskip("pyarrow")
+
+        df = DataFrame({"a": [1, 2], "c": [0, 2], "d": ["c", "a"]})
+
+        df_arrow = df.convert_dtypes(dtype_backend="pyarrow")
+        result = df_arrow.iloc[:, df_arrow["c"]]
+        expected = df_arrow.iloc[:, [0, 2]]
+        tm.assert_frame_equal(result, expected)