Ticket #17851: total_ordering.diff

django/utils/functional.py

@@ -310 +310 @@
     for item in values:
         results[predicate(item)].append(item)
     return results
+
+try:
+    from functools import total_ordering
+except ImportError:
+    # For Python < 2.7
+    def total_ordering(cls):
+        """Class decorator that fills in missing ordering methods"""
+        convert = {
+            '__lt__': [('__gt__', lambda self, other: not (self < other or self == other)),
+                       ('__le__', lambda self, other: self < other or self == other),
+                       ('__ge__', lambda self, other: not self < other)],
+            '__le__': [('__ge__', lambda self, other: not self <= other or self == other),
+                       ('__lt__', lambda self, other: self <= other and not self == other),
+                       ('__gt__', lambda self, other: not self <= other)],
+            '__gt__': [('__lt__', lambda self, other: not (self > other or self == other)),
+                       ('__ge__', lambda self, other: self > other or self == other),
+                       ('__le__', lambda self, other: not self > other)],
+            '__ge__': [('__le__', lambda self, other: (not self >= other) or self == other),
+                       ('__gt__', lambda self, other: self >= other and not self == other),
+                       ('__lt__', lambda self, other: not self >= other)]
+        }
+        roots = set(dir(cls)) & set(convert)
+        if not roots:
+            raise ValueError('must define at least one ordering operation: < > <= >=')
+        root = max(roots)       # prefer __lt__ to __le__ to __gt__ to __ge__
+        for opname, opfunc in convert[root]:
+            if opname not in roots:
+                opfunc.__name__ = opname
+                opfunc.__doc__ = getattr(int, opname).__doc__
+                setattr(cls, opname, opfunc)
+        return cls