Issue #11707: Fast C version of functools.cmp_to_key()

Lib/functools.py

@@ -97,7 +97,7 @@ def cmp_to_key(mycmp):
     """Convert a cmp= function into a key= function"""
     class K(object):
         __slots__ = ['obj']
-        def __init__(self, obj, *args):
+        def __init__(self, obj):
             self.obj = obj
         def __lt__(self, other):
             return mycmp(self.obj, other.obj) < 0
@@ -115,6 +115,11 @@ def cmp_to_key(mycmp):
             raise TypeError('hash not implemented')
     return K
 
+try:
+    from _functools import cmp_to_key
+except ImportError:
+    pass
+
 _CacheInfo = namedtuple("CacheInfo", "hits misses maxsize currsize")
 
 def lru_cache(maxsize=100):

Lib/test/test_functools.py

@@ -435,18 +435,81 @@ class TestReduce(unittest.TestCase):
         self.assertEqual(self.func(add, d), "".join(d.keys()))
 
 class TestCmpToKey(unittest.TestCase):
+
     def test_cmp_to_key(self):
+        def cmp1(x, y):
+            return (x > y) - (x < y)
+        key = functools.cmp_to_key(cmp1)
+        self.assertEqual(key(3), key(3))
+        self.assertGreater(key(3), key(1))
+        def cmp2(x, y):
+            return int(x) - int(y)
+        key = functools.cmp_to_key(cmp2)
+        self.assertEqual(key(4.0), key('4'))
+        self.assertLess(key(2), key('35'))
+
+    def test_cmp_to_key_arguments(self):
+        def cmp1(x, y):
+            return (x > y) - (x < y)
+        key = functools.cmp_to_key(mycmp=cmp1)
+        self.assertEqual(key(obj=3), key(obj=3))
+        self.assertGreater(key(obj=3), key(obj=1))
+        with self.assertRaises((TypeError, AttributeError)):
+            key(3) > 1    # rhs is not a K object
+        with self.assertRaises((TypeError, AttributeError)):
+            1 < key(3)    # lhs is not a K object
+        with self.assertRaises(TypeError):
+            key = functools.cmp_to_key()             # too few args
+        with self.assertRaises(TypeError):
+            key = functools.cmp_to_key(cmp1, None)   # too many args
+        key = functools.cmp_to_key(cmp1)
+        with self.assertRaises(TypeError):
+            key()                                    # too few args
+        with self.assertRaises(TypeError):
+            key(None, None)                          # too many args
+
+    def test_bad_cmp(self):
+        def cmp1(x, y):
+            raise ZeroDivisionError
+        key = functools.cmp_to_key(cmp1)
+        with self.assertRaises(ZeroDivisionError):
+            key(3) > key(1)
+
+        class BadCmp:
+            def __lt__(self, other):
+                raise ZeroDivisionError
+        def cmp1(x, y):
+            return BadCmp()
+        with self.assertRaises(ZeroDivisionError):
+            key(3) > key(1)
+
+    def test_obj_field(self):
+        def cmp1(x, y):
+            return (x > y) - (x < y)
+        key = functools.cmp_to_key(mycmp=cmp1)
+        self.assertEqual(key(50).obj, 50)
+
+    def test_sort_int(self):
         def mycmp(x, y):
             return y - x
         self.assertEqual(sorted(range(5), key=functools.cmp_to_key(mycmp)),
                          [4, 3, 2, 1, 0])
 
+    def test_sort_int_str(self):
+        def mycmp(x, y):
+            x, y = int(x), int(y)
+            return (x > y) - (x < y)
+        values = [5, '3', 7, 2, '0', '1', 4, '10', 1]
+        values = sorted(values, key=functools.cmp_to_key(mycmp))
+        self.assertEqual([int(value) for value in values],
+                         [0, 1, 1, 2, 3, 4, 5, 7, 10])
+
     def test_hash(self):
         def mycmp(x, y):
             return y - x
         key = functools.cmp_to_key(mycmp)
         k = key(10)
-        self.assertRaises(TypeError, hash(k))
+        self.assertRaises(TypeError, hash, k)
 
 class TestTotalOrdering(unittest.TestCase):
 
@@ -655,6 +718,7 @@ class TestLRU(unittest.TestCase):
 
 def test_main(verbose=None):
     test_classes = (
+        TestCmpToKey,
         TestPartial,
         TestPartialSubclass,
         TestPythonPartial,