added a test for issue pandas-dev#20627

Author: OlivierLuG

pandas/tests/frame/test_nonunique_indexes.py

@@ -513,3 +513,23 @@ def test_set_value_by_index(self):
 
         df.iloc[:, 0] = 3
         tm.assert_series_equal(df.iloc[:, 1], expected)
+
+
+def test_iloc_with_boolean_operation():
+    # GH 20627
+    result = DataFrame([[0, 1], [2, 3], [4, 5], [6, np.nan]])
+    result.iloc[result.index <= 2] *= 2
+    expected = DataFrame([[0, 2], [4, 6], [8, 10], [6, np.nan]])
+    tm.assert_frame_equal(result, expected)
+
+    result.iloc[result.index > 2] *= 2
+    expected = DataFrame([[0, 2], [4, 6], [8, 10], [12, np.nan]])
+    tm.assert_frame_equal(result, expected)
+
+    result.iloc[[True, True, False, False]] *= 2
+    expected = DataFrame([[0, 4], [8, 12], [8, 10], [12, np.nan]])
+    tm.assert_frame_equal(result, expected)
+
+    result.iloc[[False, False, True, True]] /= 2
+    expected = DataFrame([[0.0, 4.0], [8.0, 12.0], [4.0, 5.0], [6.0, np.nan]])
+    tm.assert_frame_equal(result, expected)