Close #18508 -- fix _value2member_map to always have the member's value

Lib/enum.py

@@ -1,5 +1,3 @@
-"""Python Enumerations"""
-
 import sys
 from collections import OrderedDict
 from types import MappingProxyType
@@ -154,11 +152,13 @@ class EnumMeta(type):
                 args = (args, )     # wrap it one more time
             if not use_args:
                 enum_member = __new__(enum_class)
-                enum_member._value = value
+                original_value = value
             else:
                 enum_member = __new__(enum_class, *args)
-                if not hasattr(enum_member, '_value'):
-                    enum_member._value = member_type(*args)
+                original_value = member_type(*args)
+            if not hasattr(enum_member, '_value'):
+                enum_member._value = original_value
+            value = enum_member._value
             enum_member._member_type = member_type
             enum_member._name = member_name
             enum_member.__init__(*args)
@@ -416,12 +416,14 @@ class Enum(metaclass=EnumMeta):
             return value
         # by-value search for a matching enum member
         # see if it's in the reverse mapping (for hashable values)
-        if value in cls._value2member_map:
-            return cls._value2member_map[value]
-        # not there, now do long search -- O(n) behavior
-        for member in cls._member_map.values():
-            if member.value == value:
-                return member
+        try:
+            if value in cls._value2member_map:
+                return cls._value2member_map[value]
+        except TypeError:
+            # not there, now do long search -- O(n) behavior
+            for member in cls._member_map.values():
+                if member.value == value:
+                    return member
         raise ValueError("%s is not a valid %s" % (value, cls.__name__))
 
     def __repr__(self):

Lib/test/test_enum.py

@@ -694,6 +694,7 @@ class TestEnum(unittest.TestCase):
             x = ('the-x', 1)
             y = ('the-y', 2)
 
+
         self.assertIs(NEI.__new__, Enum.__new__)
         self.assertEqual(repr(NEI.x + NEI.y), "NamedInt('(the-x + the-y)', 3)")
         globals()['NamedInt'] = NamedInt
@@ -785,6 +786,7 @@ class TestEnum(unittest.TestCase):
                 [AutoNumber.first, AutoNumber.second, AutoNumber.third],
                 )
         self.assertEqual(int(AutoNumber.second), 2)
+        self.assertEqual(AutoNumber.third.value, 3)
         self.assertIs(AutoNumber(1), AutoNumber.first)
 
     def test_inherited_new_from_enhanced_enum(self):
@@ -916,6 +918,22 @@ class TestEnum(unittest.TestCase):
         self.assertEqual(round(Planet.EARTH.surface_gravity, 2), 9.80)
         self.assertEqual(Planet.EARTH.value, (5.976e+24, 6.37814e6))
 
+    def test_nonhash_value(self):
+        class AutoNumberInAList(Enum):
+            def __new__(cls):
+                value = [len(cls.__members__) + 1]
+                obj = object.__new__(cls)
+                obj._value = value
+                return obj
+        class ColorInAList(AutoNumberInAList):
+            red = ()
+            green = ()
+            blue = ()
+        self.assertEqual(list(ColorInAList), [ColorInAList.red, ColorInAList.green, ColorInAList.blue])
+        self.assertEqual(ColorInAList.red.value, [1])
+        self.assertEqual(ColorInAList([1]), ColorInAList.red)
+
+
 
 class TestUnique(unittest.TestCase):