Add missing cmp_to_key for Py2.6 (issue #189)

Author: edschofield

docs/whatsnew.rst

@@ -31,6 +31,7 @@ This releases fixes also these bugs:
 - Fix `standard_library.install_aliases()` on PyPy. (Issue #205)
 - Fix assertRaises for `pow` and `compile` on Python 3.5. (Issue #183)
 - Fix return argument of `future.utils.ensure_new_type` if conversion to new type does not exist. (Issue #185)
+- Add missing `cmp_to_key` for Py2.6. (Issue #189)
 - Allow the `old_div` fixer to be disabled. (Issue #190)
 
 What's new in version 0.15.2 (2015-09-11)

src/future/__init__.py

@@ -86,8 +86,8 @@
 __license__ = 'MIT'
 __copyright__ = 'Copyright 2013-2016 Python Charmers Pty Ltd'
 __ver_major__ = 0
-__ver_minor__ = 15
-__ver_patch__ = 3
+__ver_minor__ = 16
+__ver_patch__ = 0
 __ver_sub__ = '-dev'
 __version__ = "%d.%d.%d%s" % (__ver_major__, __ver_minor__,
                               __ver_patch__, __ver_sub__)

src/future/backports/__init__.py

@@ -22,4 +22,5 @@
                    count,
                    recursive_repr,
                    _count_elements,
+                   cmp_to_key
                   )

src/future/backports/misc.py

@@ -9,7 +9,9 @@
 - itertools.count          (for Python 2.6, with step parameter)
 - subprocess.check_output  (for Python 2.6)
 - reprlib.recursive_repr   (for Python 2.6+)
+- functools.cmp_to_key     (for Python 2.6)
 """
+
 from __future__ import absolute_import
 
 import subprocess
@@ -881,6 +883,28 @@ def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT,
     else:
         raise error("getaddrinfo returns an empty list")
 
+# Backport from Py2.7 for Py2.6:
+def cmp_to_key(mycmp):
+    """Convert a cmp= function into a key= function"""
+    class K(object):
+        __slots__ = ['obj']
+        def __init__(self, obj, *args):
+            self.obj = obj
+        def __lt__(self, other):
+            return mycmp(self.obj, other.obj) < 0
+        def __gt__(self, other):
+            return mycmp(self.obj, other.obj) > 0
+        def __eq__(self, other):
+            return mycmp(self.obj, other.obj) == 0
+        def __le__(self, other):
+            return mycmp(self.obj, other.obj) <= 0
+        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')
+    return K
 
 # Back up our definitions above in case they're useful
 _OrderedDict = OrderedDict
@@ -892,6 +916,7 @@ def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT,
 _recursive_repr = recursive_repr
 _ChainMap = ChainMap
 _create_connection = create_connection
+_cmp_to_key = cmp_to_key
 
 # Overwrite the definitions above with the usual ones
 # from the standard library:
@@ -900,6 +925,7 @@ def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT,
     from subprocess import check_output
     from itertools import count
     from socket import create_connection
+    from functools import cmp_to_key
 
 if sys.version_info >= (3, 0):
     from math import ceil

src/future/standard_library/__init__.py

@@ -197,6 +197,7 @@
          ('collections', 'Counter', 'future.backports.misc', 'Counter'),
          ('itertools', 'count', 'future.backports.misc', 'count'),
          ('reprlib', 'recursive_repr', 'future.backports.misc', 'recursive_repr'),
+         ('functools', 'cmp_to_key', 'future.backports.misc', 'cmp_to_key'),
 
 # This is no use, since "import urllib.request" etc. still fails:
 #          ('urllib', 'error', 'future.moves.urllib', 'error'),