Issue #26983: float() now always return an instance of exact float.

The deprecation warning is emitted if __float__ returns an instance of
a strict subclass of float.  In a future versions of Python this can
be an error.

2 files changed, 17 insertions, 10 deletions

diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
index 427f044..68b212e 100644
--- a/Lib/test/test_float.py
+++ b/Lib/test/test_float.py
@@ -161,11 +161,12 @@ class GeneralFloatCases(unittest.TestCase):
             def __float__(self):
                 return float(str(self)) + 1
 
-        self.assertAlmostEqual(float(Foo1()), 42.)
-        self.assertAlmostEqual(float(Foo2()), 42.)
-        self.assertAlmostEqual(float(Foo3(21)), 42.)
+        self.assertEqual(float(Foo1()), 42.)
+        self.assertEqual(float(Foo2()), 42.)
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(float(Foo3(21)), 42.)
         self.assertRaises(TypeError, float, Foo4(42))
-        self.assertAlmostEqual(float(FooStr('8')), 9.)
+        self.assertEqual(float(FooStr('8')), 9.)
 
         class Foo5:
             def __float__(self):
@@ -176,10 +177,14 @@ class GeneralFloatCases(unittest.TestCase):
         class F:
             def __float__(self):
                 return OtherFloatSubclass(42.)
-        self.assertAlmostEqual(float(F()), 42.)
-        self.assertIs(type(float(F())), OtherFloatSubclass)
-        self.assertAlmostEqual(FloatSubclass(F()), 42.)
-        self.assertIs(type(FloatSubclass(F())), FloatSubclass)
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(float(F()), 42.)
+        with self.assertWarns(DeprecationWarning):
+            self.assertIs(type(float(F())), float)
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(FloatSubclass(F()), 42.)
+        with self.assertWarns(DeprecationWarning):
+            self.assertIs(type(FloatSubclass(F())), FloatSubclass)
 
     def test_is_integer(self):
         self.assertFalse((1.1).is_integer())
diff --git a/Lib/test/test_getargs2.py b/Lib/test/test_getargs2.py
index 8a51e0b..ecc1908 100644
--- a/Lib/test/test_getargs2.py
+++ b/Lib/test/test_getargs2.py
@@ -365,7 +365,8 @@ class Float_TestCase(unittest.TestCase):
         self.assertEqual(getargs_f(FloatSubclass(7.5)), 7.5)
         self.assertEqual(getargs_f(FloatSubclass2(7.5)), 7.5)
         self.assertRaises(TypeError, getargs_f, BadFloat())
-        self.assertEqual(getargs_f(BadFloat2()), 4.25)
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(getargs_f(BadFloat2()), 4.25)
         self.assertEqual(getargs_f(BadFloat3(7.5)), 7.5)
 
         for x in (FLT_MIN, -FLT_MIN, FLT_MAX, -FLT_MAX, INF, -INF):
@@ -390,7 +391,8 @@ class Float_TestCase(unittest.TestCase):
         self.assertEqual(getargs_d(FloatSubclass(7.5)), 7.5)
         self.assertEqual(getargs_d(FloatSubclass2(7.5)), 7.5)
         self.assertRaises(TypeError, getargs_d, BadFloat())
-        self.assertEqual(getargs_d(BadFloat2()), 4.25)
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(getargs_d(BadFloat2()), 4.25)
         self.assertEqual(getargs_d(BadFloat3(7.5)), 7.5)
 
         for x in (DBL_MIN, -DBL_MIN, DBL_MAX, -DBL_MAX, INF, -INF):