Continue rolling back pep-3141 changes that changed behavior from 2.5. This

round included:
 * Revert round to its 2.6 behavior (half away from 0).
 * Because round, floor, and ceil always return float again, it's no
   longer necessary to have them delegate to __xxx___, so I've ripped
   that out of their implementations and the Real ABC. This also helps
   in implementing types that work in both 2.6 and 3.0: you return int
   from the __xxx__ methods, and let it get enabled by the version
   upgrade.
 * Make pow(-1, .5) raise a ValueError again.

Lib/numbers.py

@@ -189,25 +189,6 @@ class Real(Complex):
         """
         raise NotImplementedError
 
-    @abstractmethod
-    def __floor__(self):
-        """Finds the greatest Integral <= self."""
-        raise NotImplementedError
-
-    @abstractmethod
-    def __ceil__(self):
-        """Finds the least Integral >= self."""
-        raise NotImplementedError
-
-    @abstractmethod
-    def __round__(self, ndigits=None):
-        """Rounds self to ndigits decimal places, defaulting to 0.
-
-        If ndigits is omitted or None, returns an Integral, otherwise
-        returns a Real. Rounds half toward even.
-        """
-        raise NotImplementedError
-
     def __divmod__(self, other):
         """divmod(self, other): The pair (self // other, self % other).
 

Lib/test/test_builtin.py

@@ -1456,13 +1456,12 @@ class BuiltinTest(unittest.TestCase):
                     else:
                         self.assertAlmostEqual(pow(x, y, z), 24.0)
 
-        self.assertAlmostEqual(pow(-1, 0.5), 1j)
-        self.assertAlmostEqual(pow(-1, 1./3), 0.5 + 0.8660254037844386j)
-
         self.assertRaises(TypeError, pow, -1, -2, 3)
         self.assertRaises(ValueError, pow, 1, 2, 0)
         self.assertRaises(TypeError, pow, -1L, -2L, 3L)
         self.assertRaises(ValueError, pow, 1L, 2L, 0L)
+        # Will return complex in 3.0:
+        self.assertRaises(ValueError, pow, -342.43, 0.234)
 
         self.assertRaises(TypeError, pow)
 
@@ -1664,11 +1663,11 @@ class BuiltinTest(unittest.TestCase):
         self.assertEqual(type(round(-8.0, 0)), float)
         self.assertEqual(type(round(-8.0, 1)), float)
 
-        # Check even / odd rounding behaviour
+        # Check half rounding behaviour.
         self.assertEqual(round(5.5), 6)
-        self.assertEqual(round(6.5), 6)
+        self.assertEqual(round(6.5), 7)
         self.assertEqual(round(-5.5), -6)
-        self.assertEqual(round(-6.5), -6)
+        self.assertEqual(round(-6.5), -7)
 
         # Check behavior on ints
         self.assertEqual(round(0), 0)
@@ -1686,8 +1685,8 @@ class BuiltinTest(unittest.TestCase):
 
         # test generic rounding delegation for reals
         class TestRound(object):
-            def __round__(self):
-                return 23
+            def __float__(self):
+                return 23.0
 
         class TestNoRound(object):
             pass
@@ -1695,13 +1694,12 @@ class BuiltinTest(unittest.TestCase):
         self.assertEqual(round(TestRound()), 23)
 
         self.assertRaises(TypeError, round, 1, 2, 3)
-        # XXX: This is not ideal, but see the comment in builtin_round().
-        self.assertRaises(AttributeError, round, TestNoRound())
+        self.assertRaises(TypeError, round, TestNoRound())
 
         t = TestNoRound()
-        t.__round__ = lambda *args: args
-        self.assertEquals((), round(t))
-        self.assertEquals((0,), round(t, 0))
+        t.__float__ = lambda *args: args
+        self.assertRaises(TypeError, round, t)
+        self.assertRaises(TypeError, round, t, 0)
 
     def test_setattr(self):
         setattr(sys, 'spam', 1)

Lib/test/test_long.py

@@ -385,9 +385,7 @@ class LongTest(unittest.TestCase):
                      "1. ** huge", "huge ** 1.", "1. ** mhuge", "mhuge ** 1.",
                      "math.sin(huge)", "math.sin(mhuge)",
                      "math.sqrt(huge)", "math.sqrt(mhuge)", # should do better
-                     # math.floor() of an int returns an int now
-                     ##"math.floor(huge)", "math.floor(mhuge)",
-                     ]:
+                     "math.floor(huge)", "math.floor(mhuge)"]:
 
             self.assertRaises(OverflowError, eval, test, namespace)
 

Lib/test/test_math.py

@@ -63,8 +63,8 @@ class MathTests(unittest.TestCase):
         self.ftest('ceil(-1.5)', math.ceil(-1.5), -1)
 
         class TestCeil(object):
-            def __ceil__(self):
-                return 42
+            def __float__(self):
+                return 41.3
         class TestNoCeil(object):
             pass
         self.ftest('ceil(TestCeil())', math.ceil(TestCeil()), 42)
@@ -123,8 +123,8 @@ class MathTests(unittest.TestCase):
         self.ftest('floor(-1.23e167)', math.floor(-1.23e167), -1.23e167)
 
         class TestFloor(object):
-            def __floor__(self):
-                return 42
+            def __float__(self):
+                return 42.3
         class TestNoFloor(object):
             pass
         self.ftest('floor(TestFloor())', math.floor(TestFloor()), 42)