bpo-44558: Make the implementation consistency of operator.indexOf (GH-27012)

(cherry picked from commit 0930240)

Co-authored-by: Dong-hee Na <[email protected]>

Author: miss-islington

Lib/operator.py

@@ -173,7 +173,7 @@ def getitem(a, b):
 def indexOf(a, b):
     "Return the first index of b in a."
     for i, j in enumerate(a):
-        if j == b:
+        if j is b or j == b:
             return i
     else:
         raise ValueError('sequence.index(x): x not in sequence')

Lib/test/test_operator.py

@@ -188,6 +188,9 @@ def test_indexOf(self):
         self.assertRaises(ZeroDivisionError, operator.indexOf, BadIterable(), 1)
         self.assertEqual(operator.indexOf([4, 3, 2, 1], 3), 1)
         self.assertRaises(ValueError, operator.indexOf, [4, 3, 2, 1], 0)
+        nan = float("nan")
+        self.assertEqual(operator.indexOf([nan, nan, 21], nan), 0)
+        self.assertEqual(operator.indexOf([{}, 1, {}, 2], {}), 0)
 
     def test_invert(self):
         operator = self.module

Misc/NEWS.d/next/Library/2021-07-04-21-16-53.bpo-44558.cm7Slv.rst

@@ -0,0 +1,2 @@
+Make the implementation consistency of :func:`~operator.indexOf` between
+C and Python versions. Patch by Dong-hee Na.