[Enum] Make some private attributes public.

- ``_EnumDict`` --> ``EnumDict``
- ``EnumDict._member_names`` --> ``EnumDict.member_names``
- ``EnumType._add_alias_``
- ``EnumType._add_value_alias_``

Author: ethanfurman

Doc/howto/enum.rst

@@ -868,16 +868,16 @@ Others
 While :class:`IntEnum` is part of the :mod:`enum` module, it would be very
 simple to implement independently::
 
-    class IntEnum(int, Enum):
+    class IntEnum(int, ReprEnum):   # or Enum instead of ReprEnum
         pass
 
 This demonstrates how similar derived enumerations can be defined; for example
 a :class:`FloatEnum` that mixes in :class:`float` instead of :class:`int`.
 
 Some rules:
 
-1. When subclassing :class:`Enum`, mix-in types must appear before
-   :class:`Enum` itself in the sequence of bases, as in the :class:`IntEnum`
+1. When subclassing :class:`Enum`, mix-in types must appear before the
+   :class:`Enum` class itself in the sequence of bases, as in the :class:`IntEnum`
    example above.
 2. Mix-in types must be subclassable. For example, :class:`bool` and
    :class:`range` are not subclassable and will throw an error during Enum
@@ -961,30 +961,36 @@ all the members are created it is no longer used.
 Supported ``_sunder_`` names
 """"""""""""""""""""""""""""
 
-- ``_name_`` -- name of the member
-- ``_value_`` -- value of the member; can be set / modified in ``__new__``
-
-- ``_missing_`` -- a lookup function used when a value is not found; may be
-  overridden
-- ``_ignore_`` -- a list of names, either as a :class:`list` or a :class:`str`,
-  that will not be transformed into members, and will be removed from the final
-  class
-- ``_order_`` -- used in Python 2/3 code to ensure member order is consistent
-  (class attribute, removed during class creation)
-- ``_generate_next_value_`` -- used by the `Functional API`_ and by
-  :class:`auto` to get an appropriate value for an enum member; may be
-  overridden
-
-.. note::
-
-    For standard :class:`Enum` classes the next value chosen is the last value seen
-    incremented by one.
-
-    For :class:`Flag` classes the next value chosen will be the next highest
-    power-of-two, regardless of the last value seen.
+- :meth:`~EnumType._add_alias_` -- adds a new name as an alias to an existing
+  member.
+- :meth:`~EnumType._add_value_alias_` -- adds a new value as an alias to an
+  existing member.
+- :attr:`~Enum._name_` -- name of the member
+- :attr:`~Enum._value_` -- value of the member; can be set in ``__new__``
+- :meth:`~Enum._missing_` -- a lookup function used when a value is not found;
+  may be overridden
+- :attr:`~Enum._ignore_` -- a list of names, either as a :class:`list` or a
+  :class:`str`, that will not be transformed into members, and will be removed
+  from the final class
+- :attr:`~Enum._order_` -- used in Python 2/3 code to ensure member order is
+  consistent (class attribute, removed during class creation)
+- :meth:`~Enum._generate_next_value_` -- used to get an appropriate value for
+  an enum member; may be overridden
+
+  .. note::
+
+     For standard :class:`Enum` classes the next value chosen is the highest
+     value seen incremented by one.
+
+     For :class:`Flag` classes the next value chosen will be the next highest
+     power-of-two.
+
+  .. versionchanged:: 3.13
+     Prior versions would use the last seen value instead of the highest value.
 
 .. versionadded:: 3.6 ``_missing_``, ``_order_``, ``_generate_next_value_``
 .. versionadded:: 3.7 ``_ignore_``
+.. versionadded:: 3.13 ``_add_alias_``, ``_add_value_alias_``
 
 To help keep Python 2 / Python 3 code in sync an :attr:`_order_` attribute can
 be provided.  It will be checked against the actual order of the enumeration

Doc/library/enum.rst

@@ -235,16 +235,30 @@ Data Types
         >>> len(Color)
         3
 
+   .. attribute: EnumType.__members__
+
+      Returns a mapping of every enum name to its member, including aliases
+
    .. method:: EnumType.__reversed__(cls)
 
       Returns each member in *cls* in reverse definition order::
 
         >>> list(reversed(Color))
         [<Color.BLUE: 3>, <Color.GREEN: 2>, <Color.RED: 1>]
 
+   .. method: EnumType._add_alias_
+
+      Adds a new name as an alias to an existing member.  Raises a
+      :exc:`NameError` if the name is already assigned to a different member.
+
+   .. method: EnumType._add_value_alias_
+
+      Adds a new value as an alias to an existing member.  Raises a
+      :exc:`ValueError` if the value is already linked with a different member.
+
    .. versionadded:: 3.11
 
-      Before 3.11 ``enum`` used ``EnumMeta`` type, which is kept as an alias.
+      Before 3.11 ``EnumType`` was called ``EnumMeta``, which is still available as an alias.
 
 
 .. class:: Enum
@@ -323,7 +337,7 @@ Data Types
          >>> PowersOfThree.SECOND.value
          9
 
-   .. method:: Enum.__init_subclass__(cls, **kwds)
+   .. method:: Enum.__init_subclass__(cls, \**kwds)
 
       A *classmethod* that is used to further configure subsequent subclasses.
       By default, does nothing.
@@ -549,7 +563,7 @@ Data Types
 
    .. method:: __invert__(self):
 
-      Returns all the flags in *type(self)* that are not in self::
+      Returns all the flags in *type(self)* that are not in *self*::
 
          >>> ~white
          <Color: 0>
@@ -769,37 +783,41 @@ Supported ``__dunder__`` names
 :attr:`~EnumType.__members__` is a read-only ordered mapping of ``member_name``:``member``
 items.  It is only available on the class.
 
-:meth:`~object.__new__`, if specified, must create and return the enum members; it is
-also a very good idea to set the member's :attr:`!_value_` appropriately.  Once
-all the members are created it is no longer used.
+:meth:`~object.__new__`, if specified, must create and return the enum members;
+it is also a very good idea to set the member's :attr:`!_value_` appropriately.
+Once all the members are created it is no longer used.
 
 
 Supported ``_sunder_`` names
 """"""""""""""""""""""""""""
 
-- ``_name_`` -- name of the member
-- ``_value_`` -- value of the member; can be set / modified in ``__new__``
-
-- ``_missing_`` -- a lookup function used when a value is not found; may be
-  overridden
-- ``_ignore_`` -- a list of names, either as a :class:`list` or a :class:`str`,
-  that will not be transformed into members, and will be removed from the final
-  class
-- ``_order_`` -- used in Python 2/3 code to ensure member order is consistent
-  (class attribute, removed during class creation)
-- ``_generate_next_value_`` -- used to get an appropriate value for an enum
-  member; may be overridden
+- :meth:`~EnumType._add_alias_` -- adds a new name as an alias to an existing
+  member.
+- :meth:`~EnumType._add_value_alias_` -- adds a new value as an alias to an
+  existing member.
+- :attr:`~Enum._name_` -- name of the member
+- :attr:`~Enum._value_` -- value of the member; can be set in ``__new__``
+- :meth:`~Enum._missing_` -- a lookup function used when a value is not found;
+  may be overridden
+- :attr:`~Enum._ignore_` -- a list of names, either as a :class:`list` or a
+  :class:`str`, that will not be transformed into members, and will be removed
+  from the final class
+- :attr:`~Enum._order_` -- used in Python 2/3 code to ensure member order is
+  consistent (class attribute, removed during class creation)
+- :meth:`~Enum._generate_next_value_` -- used to get an appropriate value for
+  an enum member; may be overridden
 
   .. note::
 
-     For standard :class:`Enum` classes the next value chosen is the last value seen
-     incremented by one.
+     For standard :class:`Enum` classes the next value chosen is the highest
+     value seen incremented by one.
 
      For :class:`Flag` classes the next value chosen will be the next highest
-     power-of-two, regardless of the last value seen.
+     power-of-two.
 
 .. versionadded:: 3.6 ``_missing_``, ``_order_``, ``_generate_next_value_``
 .. versionadded:: 3.7 ``_ignore_``
+.. versionadded:: 3.13 ``_add_alias_``, ``_add_value_alias_``
 
 ---------------
 

Lib/enum.py

@@ -4,7 +4,7 @@
 
 
 __all__ = [
-        'EnumType', 'EnumMeta',
+        'EnumType', 'EnumMeta', 'EnumDict',
         'Enum', 'IntEnum', 'StrEnum', 'Flag', 'IntFlag', 'ReprEnum',
         'auto', 'unique', 'property', 'verify', 'member', 'nonmember',
         'FlagBoundary', 'STRICT', 'CONFORM', 'EJECT', 'KEEP',
@@ -313,45 +313,8 @@ def __set_name__(self, enum_class, member_name):
                 ):
                 # no other instances found, record this member in _member_names_
                 enum_class._member_names_.append(member_name)
-        # if necessary, get redirect in place and then add it to _member_map_
-        found_descriptor = None
-        descriptor_type = None
-        class_type = None
-        for base in enum_class.__mro__[1:]:
-            attr = base.__dict__.get(member_name)
-            if attr is not None:
-                if isinstance(attr, (property, DynamicClassAttribute)):
-                    found_descriptor = attr
-                    class_type = base
-                    descriptor_type = 'enum'
-                    break
-                elif _is_descriptor(attr):
-                    found_descriptor = attr
-                    descriptor_type = descriptor_type or 'desc'
-                    class_type = class_type or base
-                    continue
-                else:
-                    descriptor_type = 'attr'
-                    class_type = base
-        if found_descriptor:
-            redirect = property()
-            redirect.member = enum_member
-            redirect.__set_name__(enum_class, member_name)
-            if descriptor_type in ('enum','desc'):
-                # earlier descriptor found; copy fget, fset, fdel to this one.
-                redirect.fget = getattr(found_descriptor, 'fget', None)
-                redirect._get = getattr(found_descriptor, '__get__', None)
-                redirect.fset = getattr(found_descriptor, 'fset', None)
-                redirect._set = getattr(found_descriptor, '__set__', None)
-                redirect.fdel = getattr(found_descriptor, 'fdel', None)
-                redirect._del = getattr(found_descriptor, '__delete__', None)
-            redirect._attr_type = descriptor_type
-            redirect._cls_type = class_type
-            setattr(enum_class, member_name, redirect)
-        else:
-            setattr(enum_class, member_name, enum_member)
-        # now add to _member_map_ (even aliases)
-        enum_class._member_map_[member_name] = enum_member
+
+        enum_class._add_member_(enum_member, member_name)
         try:
             # This may fail if value is not hashable. We can't add the value
             # to the map, and by-value lookups for this value will be
@@ -362,7 +325,7 @@ def __set_name__(self, enum_class, member_name):
             enum_class._unhashable_values_.append(value)
 
 
-class _EnumDict(dict):
+class EnumDict(dict):
     """
     Track enum member order and ensure member names are not reused.
 
@@ -371,7 +334,7 @@ class _EnumDict(dict):
     """
     def __init__(self):
         super().__init__()
-        self._member_names = {} # use a dict to keep insertion order
+        self._member_names = {} # use a dict -- faster look-up than a list, and keeps insertion order since 3.7 (?)
         self._last_values = []
         self._ignore = []
         self._auto_called = False
@@ -468,6 +431,10 @@ def __setitem__(self, key, value):
                 self._last_values.append(value)
         super().__setitem__(key, value)
 
+    @property
+    def member_names(self):
+        return list(self._member_names)
+
     def update(self, members, **more_members):
         try:
             for name in members.keys():
@@ -478,6 +445,8 @@ def update(self, members, **more_members):
         for name, value in more_members.items():
             self[name] = value
 
+_EnumDict = EnumDict        # keep private name for backwards compatibility
+
 
 class EnumType(type):
     """
@@ -489,7 +458,7 @@ def __prepare__(metacls, cls, bases, **kwds):
         # check that previous enum members do not exist
         metacls._check_for_existing_members_(cls, bases)
         # create the namespace dict
-        enum_dict = _EnumDict()
+        enum_dict = EnumDict()
         enum_dict._cls_name = cls
         # inherit previous flags and _generate_next_value_ function
         member_type, first_enum = metacls._get_mixins_(cls, bases)
@@ -1046,7 +1015,80 @@ def _find_new_(mcls, classdict, member_type, first_enum):
         else:
             use_args = True
         return __new__, save_new, use_args
-EnumMeta = EnumType
+
+    def _add_alias_(cls, member, name):
+        if name in cls._member_map_:
+            if cls._member_map_[name] is not member:
+                raise NameError('%r is already bound: %r' % (name, cls._member_map_[name]))
+            return
+        #
+        # if necessary, get redirect in place and then add it to _member_map_
+        found_descriptor = None
+        descriptor_type = None
+        class_type = None
+        for base in cls.__mro__[1:]:
+            attr = base.__dict__.get(name)
+            if attr is not None:
+                if isinstance(attr, (property, DynamicClassAttribute)):
+                    found_descriptor = attr
+                    class_type = base
+                    descriptor_type = 'enum'
+                    break
+                elif _is_descriptor(attr):
+                    found_descriptor = attr
+                    descriptor_type = descriptor_type or 'desc'
+                    class_type = class_type or base
+                    continue
+                else:
+                    descriptor_type = 'attr'
+                    class_type = base
+        if found_descriptor:
+            redirect = property()
+            redirect.member = member
+            redirect.__set_name__(cls, name)
+            if descriptor_type in ('enum','desc'):
+                # earlier descriptor found; copy fget, fset, fdel to this one.
+                redirect.fget = getattr(found_descriptor, 'fget', None)
+                redirect._get = getattr(found_descriptor, '__get__', None)
+                redirect.fset = getattr(found_descriptor, 'fset', None)
+                redirect._set = getattr(found_descriptor, '__set__', None)
+                redirect.fdel = getattr(found_descriptor, 'fdel', None)
+                redirect._del = getattr(found_descriptor, '__delete__', None)
+            redirect._attr_type = descriptor_type
+            redirect._cls_type = class_type
+            setattr(cls, name, redirect)
+        else:
+            setattr(cls, name, member)
+        # now add to _member_map_ (even aliases)
+        cls._member_map_[name] = member
+        #
+        cls._member_map_[name] = member
+    _add_member_ = _add_alias_                  # use _add_member_ internally
+
+    def _add_value_alias_(cls, member, value):
+        try:
+            if value in cls._value2member_map_:
+                if cls._value2member_map_[value] is not member:
+                    raise ValueError('%r is already bound: %r' % (value, cls._value2member_map_[value]))
+                return
+        except TypeError:
+            # unhashable value, do long search
+            for m in cls._member_map_.values():
+                if m._value_ == value:
+                    if m is not member:
+                        raise ValueError('%r is already bound: %r' % (value, cls._value2member_map_[value]))
+                    return
+        try:
+            # This may fail if value is not hashable. We can't add the value
+            # to the map, and by-value lookups for this value will be
+            # linear.
+            cls._value2member_map_.setdefault(value, member)
+        except TypeError:
+            # keep track of the value in a list so containment checks are quick
+            cls._unhashable_values_.append(value)
+
+
+EnumMeta = EnumType         # keep EnumMeta name for backwards compatibility
 
 
 class Enum(metaclass=EnumType):
@@ -1113,7 +1155,7 @@ def __new__(cls, value):
         except TypeError:
             # not there, now do long search -- O(n) behavior
             for member in cls._member_map_.values():
-                if member._value_ == value:
+                if member._value_ is value or member._value_ == value:
                     return member
         # still not found -- verify that members exist, in-case somebody got here mistakenly
         # (such as via super when trying to override __new__)