Issue #8188: Introduce a new scheme for computing hashes of numbers

(instances of int, float, complex, decimal.Decimal and
fractions.Fraction) that makes it easy to maintain the invariant that
hash(x) == hash(y) whenever x and y have equal value.

1 files changed, 17 insertions, 0 deletions

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 2caf09f..c056f9a 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -426,6 +426,23 @@ class SysModuleTest(unittest.TestCase):
         self.assertEqual(type(sys.int_info.bits_per_digit), int)
         self.assertEqual(type(sys.int_info.sizeof_digit), int)
         self.assertIsInstance(sys.hexversion, int)
+
+        self.assertEqual(len(sys.hash_info), 5)
+        self.assertLess(sys.hash_info.modulus, 2**sys.hash_info.width)
+        # sys.hash_info.modulus should be a prime; we do a quick
+        # probable primality test (doesn't exclude the possibility of
+        # a Carmichael number)
+        for x in range(1, 100):
+            self.assertEqual(
+                pow(x, sys.hash_info.modulus-1, sys.hash_info.modulus),
+                1,
+                "sys.hash_info.modulus {} is a non-prime".format(
+                    sys.hash_info.modulus)
+                )
+        self.assertIsInstance(sys.hash_info.inf, int)
+        self.assertIsInstance(sys.hash_info.nan, int)
+        self.assertIsInstance(sys.hash_info.imag, int)
+
         self.assertIsInstance(sys.maxsize, int)
         self.assertIsInstance(sys.maxunicode, int)
         self.assertIsInstance(sys.platform, str)