BUG: raise on empty sequence input to unravel_index, ravel_index_multi; clarify error msg

1 files changed, 20 insertions, 0 deletions

diff --git a/numpy/lib/tests/test_index_tricks.py b/numpy/lib/tests/test_index_tricks.py
index 3246f68ff..028bba37d 100644
--- a/numpy/lib/tests/test_index_tricks.py
+++ b/numpy/lib/tests/test_index_tricks.py
@@ -77,6 +77,26 @@ class TestRavelUnravelIndex(object):
             [[3, 6, 6], [4, 5, 1]])
         assert_equal(np.unravel_index(1621, (6, 7, 8, 9)), [3, 1, 4, 1])
 
+    def test_empty_indices(self):
+        msg1 = 'indices must be integral: the provided empty sequence was'
+        msg2 = 'only int indices permitted'
+        assert_raises_regex(TypeError, msg1, np.unravel_index, [], (10, 3, 5))
+        assert_raises_regex(TypeError, msg1, np.unravel_index, (), (10, 3, 5))
+        assert_raises_regex(TypeError, msg2, np.unravel_index, np.array([]),
+                            (10, 3, 5))
+        assert_equal(np.unravel_index(np.array([],dtype=int), (10, 3, 5)),
+                     [[], [], []])
+        assert_raises_regex(TypeError, msg1, np.ravel_multi_index, ([], []),
+                            (10, 3))
+        assert_raises_regex(TypeError, msg1, np.ravel_multi_index, ([], ['abc']),
+                            (10, 3))
+        assert_raises_regex(TypeError, msg2, np.ravel_multi_index,
+                    (np.array([]), np.array([])), (5, 3))
+        assert_equal(np.ravel_multi_index(
+                (np.array([], dtype=int), np.array([], dtype=int)), (5, 3)), [])
+        assert_equal(np.ravel_multi_index(np.array([[], []], dtype=int),
+                     (5, 3)), [])
+
     def test_big_indices(self):
         # ravel_multi_index for big indices (issue #7546)
         if np.intp == np.int64: