bpo-32856: Optimize the assignment idiom in comprehensions. (GH-16814)
Now `for y in [expr]` in comprehensions is as fast as a simple
assignment `y = expr`.
diff --git a/Lib/test/test_dictcomps.py b/Lib/test/test_dictcomps.py
index 927e310..16aa651 100644
--- a/Lib/test/test_dictcomps.py
+++ b/Lib/test/test_dictcomps.py
@@ -111,5 +111,22 @@
self.assertEqual(actual, expected)
self.assertEqual(actual_calls, expected_calls)
+ def test_assignment_idiom_in_comprehensions(self):
+ expected = {1: 1, 2: 4, 3: 9, 4: 16}
+ actual = {j: j*j for i in range(4) for j in [i+1]}
+ self.assertEqual(actual, expected)
+ expected = {3: 2, 5: 6, 7: 12, 9: 20}
+ actual = {j+k: j*k for i in range(4) for j in [i+1] for k in [j+1]}
+ self.assertEqual(actual, expected)
+ expected = {3: 2, 5: 6, 7: 12, 9: 20}
+ actual = {j+k: j*k for i in range(4) for j, k in [(i+1, i+2)]}
+ self.assertEqual(actual, expected)
+
+ def test_star_expression(self):
+ expected = {0: 0, 1: 1, 2: 4, 3: 9}
+ self.assertEqual({i: i*i for i in [*range(4)]}, expected)
+ self.assertEqual({i: i*i for i in (*range(4),)}, expected)
+
+
if __name__ == "__main__":
unittest.main()