fix random bytes generation

Author: picnixz

Lib/test/test_uuid.py

@@ -721,22 +721,23 @@ def test_uuid7(self):
         fake_nanoseconds = 1545052026752910643
         # some fake 74 = 12 + 62 random bits speared over 76 bits
         # are generated by generating a random 76-bit number, and
-        # split into chunks of 62 (hi) and 12 (lo) bits. It is a
-        rand_a = random.getrandbits(12)
-        rand_b = random.getrandbits(62)
-        fake_bytes = (rand_b << 12) | rand_a
-        fake_bytes = fake_bytes.to_bytes(19, byteorder='big')
-
-        with mock.patch.object(self.uuid, '_last_timestamp_v7', None), \
-                mock.patch('time.time_ns', return_value=fake_nanoseconds), \
-                mock.patch('os.urandom', return_value=fake_bytes):
-            u = self.uuid.uuid7()
-            equal(u.variant, self.uuid.RFC_4122)
-            equal(u.version, 7)
-            fake_milliseconds = (fake_nanoseconds // 1_000_000) & 0xffffffffffff
-            equal((u.int >> 80) & 0xffffffffffff, fake_milliseconds)
-            equal((u.int >> 64) & 0x0fff, rand_a)
-            equal(u.int & 0x3fffffffffffffff, rand_b)
+        # split into chunks of 62 (hi) and 12 (lo) bits.
+        for _ in range(100):
+            rand_a = random.getrandbits(12)
+            rand_b = random.getrandbits(62)
+            fake_bytes = (rand_b << 12) | rand_a
+            fake_bytes = fake_bytes.to_bytes(10, byteorder='big')
+
+            with mock.patch.object(self.uuid, '_last_timestamp_v7', None), \
+                    mock.patch('time.time_ns', return_value=fake_nanoseconds), \
+                    mock.patch('os.urandom', return_value=fake_bytes):
+                u = self.uuid.uuid7()
+                equal(u.variant, self.uuid.RFC_4122)
+                equal(u.version, 7)
+                fake_milliseconds = (fake_nanoseconds // 1_000_000) & 0xffffffffffff
+                equal((u.int >> 80) & 0xffffffffffff, fake_milliseconds)
+                equal((u.int >> 64) & 0x0fff, rand_a)
+                equal(u.int & 0x3fffffffffffffff, rand_b)
 
     def test_uuid8(self):
         equal = self.assertEqual

Lib/uuid.py

@@ -782,9 +782,9 @@ def uuid7():
     # Ideally, we would have 'rand_a' = first 12 bits of 'rand'
     # and 'rand_b' = lowest 62 bits, but it is easier to test
     # when we pick 'rand_a' from the lowest bits of 'rand' and
-    # 'rand_b' from the next 62 bits, ignoring the first bits
+    # 'rand_b' from the next 62 bits, ignoring the 6 first bits
     # of 'rand'.
-    rand = int.from_bytes(os.urandom(19))  # 76 random bits (ignore 2 first)
+    rand = int.from_bytes(os.urandom(10))  # 80 random bits (ignore 6 first)
     int_uuid_7 |= (rand & 0x0fff) << 64  # rand_a
     int_uuid_7 |= (rand >> 12) & 0x3fffffffffffffff  # rand_b
     return UUID(int=int_uuid_7, version=7)