Fix __hash__ in functools.cmp_to_key() to work with collections.Hashable.

Author: rhettinger

Lib/functools.py

@@ -111,8 +111,7 @@ def __ge__(self, other):
             return mycmp(self.obj, other.obj) >= 0
         def __ne__(self, other):
             return mycmp(self.obj, other.obj) != 0
-        def __hash__(self):
-            raise TypeError('hash not implemented')
+        __hash__ = None
     return K
 
 _CacheInfo = namedtuple("CacheInfo", "hits misses maxsize currsize")

Lib/test/test_functools.py

@@ -1,4 +1,5 @@
 import functools
+import collections
 import sys
 import unittest
 from test import support
@@ -446,7 +447,8 @@ 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)
+        self.assertFalse(isinstance(k, collections.Hashable))
 
 class TestTotalOrdering(unittest.TestCase):
 
@@ -660,6 +662,7 @@ def test_main(verbose=None):
         TestPythonPartial,
         TestUpdateWrapper,
         TestTotalOrdering,
+        TestCmpToKey,
         TestWraps,
         TestReduce,
         TestLRU,

Misc/NEWS

@@ -81,6 +81,8 @@ Library
 
 - logging: don't define QueueListener if Python has no thread support.
 
+- functools.cmp_to_key() now works with collections.Hashable().
+
 - Issue #11277: mmap.mmap() calls fcntl(fd, F_FULLFSYNC) on Mac OS X to get
   around a mmap bug with sparse files. Patch written by Steffen Daode Nurpmeso.