1 files changed, 16 insertions, 4 deletions
diff --git a/Lib/enum.py b/Lib/enum.py
index b8787d19b8..99db9e6b7f 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -1,8 +1,14 @@
 import sys
-from collections import OrderedDict
 from types import MappingProxyType, DynamicClassAttribute
 
-__all__ = ['Enum', 'IntEnum', 'unique']
+# try _collections first to reduce startup cost
+try:
+    from _collections import OrderedDict
+except ImportError:
+    from collections import OrderedDict
+
+
+__all__ = ['EnumMeta', 'Enum', 'IntEnum', 'unique']
 
 
 def _is_descriptor(obj):
@@ -544,8 +550,14 @@ class Enum(metaclass=EnumMeta):
             source = vars(source)
         else:
             source = module_globals
-        members = {name: value for name, value in source.items()
-                if filter(name)}
+        # We use an OrderedDict of sorted source keys so that the
+        # _value2member_map is populated in the same order every time
+        # for a consistent reverse mapping of number to name when there
+        # are multiple names for the same number rather than varying
+        # between runs due to hash randomization of the module dictionary.
+        members = OrderedDict((name, source[name])
+                              for name in sorted(source.keys())
+                              if filter(name))
         cls = cls(name, members, module=module)
         cls.__reduce_ex__ = _reduce_ex_by_name
         module_globals.update(cls.__members__)