Issue 27936: Fix inconsistent round() behavior between float and int

2 files changed, 12 insertions, 1 deletions

diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 8cc1b00..39c80b0 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -3,6 +3,8 @@
 import ast
 import builtins
 import collections
+import decimal
+import fractions
 import io
 import locale
 import os
@@ -1244,6 +1246,15 @@ class BuiltinTest(unittest.TestCase):
         self.assertEqual(round(5e15+2), 5e15+2)
         self.assertEqual(round(5e15+3), 5e15+3)
 
+    def test_bug_27936(self):
+        # Verify that ndigits=None means the same as passing in no argument
+        for x in [1234,
+                  1234.56,
+                  decimal.Decimal('1234.56'),
+                  fractions.Fraction(123456, 100)]:
+            self.assertEqual(round(x, None), round(x))
+            self.assertEqual(type(round(x, None)), type(round(x)))
+
     def test_setattr(self):
         setattr(sys, 'spam', 1)
         self.assertEqual(sys.spam, 1)
diff --git a/Lib/test/test_long.py b/Lib/test/test_long.py
index b2d008b..4b2d81c 100644
--- a/Lib/test/test_long.py
+++ b/Lib/test/test_long.py
@@ -967,7 +967,7 @@ class LongTest(unittest.TestCase):
             self.assertIs(type(got), int)
 
         # bad second argument
-        bad_exponents = ('brian', 2.0, 0j, None)
+        bad_exponents = ('brian', 2.0, 0j)
         for e in bad_exponents:
             self.assertRaises(TypeError, round, 3, e)