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Doc/library/enum.rst
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Ethan Furman
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:mod:`!enum` --- Support for enumerations
=========================================

.. module:: enum
   :synopsis: Implementation of an enumeration class.

.. moduleauthor:: Ethan Furman <ethan@stoneleaf.us>
.. sectionauthor:: Barry Warsaw <barry@python.org>
.. sectionauthor:: Eli Bendersky <eliben@gmail.com>
.. sectionauthor:: Ethan Furman <ethan@stoneleaf.us>

.. versionadded:: 3.4

**Source code:** :source:`Lib/enum.py`

.. sidebar:: Important

   This page contains the API reference information. For tutorial
   information and discussion of more advanced topics, see

   * :ref:`Basic Tutorial <enum-basic-tutorial>`
   * :ref:`Advanced Tutorial <enum-advanced-tutorial>`
   * :ref:`Enum Cookbook <enum-cookbook>`

---------------

An enumeration:

* is a set of symbolic names (members) bound to unique values
* can be iterated over to return its canonical (i.e. non-alias) members in
  definition order
* uses *call* syntax to return members by value
* uses *index* syntax to return members by name

Enumerations are created either by using :keyword:`class` syntax, or by
using function-call syntax::

   >>> from enum import Enum

   >>> # class syntax
   >>> class Color(Enum):
   ...     RED = 1
   ...     GREEN = 2
   ...     BLUE = 3

   >>> # functional syntax
   >>> Color = Enum('Color', [('RED', 1), ('GREEN', 2), ('BLUE', 3)])

Even though we can use :keyword:`class` syntax to create Enums, Enums
are not normal Python classes.  See
:ref:`How are Enums different? <enum-class-differences>` for more details.

.. note:: Nomenclature

   - The class :class:`!Color` is an *enumeration* (or *enum*)
   - The attributes :attr:`!Color.RED`, :attr:`!Color.GREEN`, etc., are
     *enumeration members* (or *members*) and are functionally constants.
   - The enum members have *names* and *values* (the name of
     :attr:`!Color.RED` is ``RED``, the value of :attr:`!Color.BLUE` is
     ``3``, etc.)

---------------

Module Contents
---------------

   :class:`EnumType`

      The ``type`` for Enum and its subclasses.

   :class:`Enum`

      Base class for creating enumerated constants.

   :class:`IntEnum`

      Base class for creating enumerated constants that are also
      subclasses of :class:`int`. (`Notes`_)

   :class:`StrEnum`

      Base class for creating enumerated constants that are also
      subclasses of :class:`str`. (`Notes`_)

   :class:`Flag`

      Base class for creating enumerated constants that can be combined using
      the bitwise operations without losing their :class:`Flag` membership.

   :class:`IntFlag`

      Base class for creating enumerated constants that can be combined using
      the bitwise operators without losing their :class:`IntFlag` membership.
      :class:`IntFlag` members are also subclasses of :class:`int`. (`Notes`_)

   :class:`ReprEnum`

      Used by :class:`IntEnum`, :class:`StrEnum`, and :class:`IntFlag`
      to keep the :class:`str() <str>` of the mixed-in type.

   :class:`EnumCheck`

      An enumeration with the values ``CONTINUOUS``, ``NAMED_FLAGS``, and
      ``UNIQUE``, for use with :func:`verify` to ensure various constraints
      are met by a given enumeration.

   :class:`FlagBoundary`

      An enumeration with the values ``STRICT``, ``CONFORM``, ``EJECT``, and
      ``KEEP`` which allows for more fine-grained control over how invalid values
      are dealt with in an enumeration.

   :class:`EnumDict`

      A subclass of :class:`dict` for use when subclassing :class:`EnumType`.

   :class:`auto`

      Instances are replaced with an appropriate value for Enum members.
      :class:`StrEnum` defaults to the lower-cased version of the member name,
      while other Enums default to 1 and increase from there.

   :func:`~enum.property`

      Allows :class:`Enum` members to have attributes without conflicting with
      member names.  The ``value`` and ``name`` attributes are implemented this
      way.

   :func:`unique`

      Enum class decorator that ensures only one name is bound to any one value.

   :func:`verify`

      Enum class decorator that checks user-selectable constraints on an
      enumeration.

   :func:`member`

      Make ``obj`` a member.  Can be used as a decorator.

   :func:`nonmember`

      Do not make ``obj`` a member.  Can be used as a decorator.

   :func:`global_enum`

      Modify the :class:`str() <str>` and :func:`repr` of an enum
      to show its members as belonging to the module instead of its class,
      and export the enum members to the global namespace.

   :func:`show_flag_values`

      Return a list of all power-of-two integers contained in a flag.


.. versionadded:: 3.6  ``Flag``, ``IntFlag``, ``auto``
.. versionadded:: 3.11  ``StrEnum``, ``EnumCheck``, ``ReprEnum``, ``FlagBoundary``, ``property``, ``member``, ``nonmember``, ``global_enum``, ``show_flag_values``
.. versionadded:: 3.13  ``EnumDict``

---------------

Data Types
----------


.. class:: EnumType

   *EnumType* is the :term:`metaclass` for *enum* enumerations.  It is possible
   to subclass *EnumType* -- see :ref:`Subclassing EnumType <enumtype-examples>`
   for details.

   ``EnumType`` is responsible for setting the correct :meth:`!__repr__`,
   :meth:`!__str__`, :meth:`!__format__`, and :meth:`!__reduce__` methods on the
   final *enum*, as well as creating the enum members, properly handling
   duplicates, providing iteration over the enum class, etc.

   .. versionadded:: 3.11

      Before 3.11 ``EnumType`` was called ``EnumMeta``, which is still available as an alias.

   .. method:: EnumType.__call__(cls, value, names=None, *, module=None, qualname=None, type=None, start=1, boundary=None)

      This method is called in two different ways:

      * to look up an existing member:

         :cls:   The enum class being called.
         :value: The value to lookup.

      * to use the ``cls`` enum to create a new enum (only if the existing enum
        does not have any members):

         :cls:   The enum class being called.
         :value: The name of the new Enum to create.
         :names: The names/values of the members for the new Enum.
         :module:    The name of the module the new Enum is created in.
         :qualname:  The actual location in the module where this Enum can be found.
         :type:  A mix-in type for the new Enum.
         :start: The first integer value for the Enum (used by :class:`auto`).
         :boundary:  How to handle out-of-range values from bit operations (:class:`Flag` only).

   .. method:: EnumType.__contains__(cls, member)

      Returns ``True`` if member belongs to the ``cls``::

        >>> some_var = Color.RED
        >>> some_var in Color
        True
        >>> Color.RED.value in Color
        True

      .. versionchanged:: 3.12

         Before Python 3.12, a ``TypeError`` is raised if a
         non-Enum-member is used in a containment check.

   .. method:: EnumType.__dir__(cls)

      Returns ``['__class__', '__doc__', '__members__', '__module__']`` and the
      names of the members in *cls*::

        >>> dir(Color)
        ['BLUE', 'GREEN', 'RED', '__class__', '__contains__', '__doc__', '__getitem__', '__init_subclass__', '__iter__', '__len__', '__members__', '__module__', '__name__', '__qualname__']

   .. method:: EnumType.__getitem__(cls, name)

      Returns the Enum member in *cls* matching *name*, or raises a :exc:`KeyError`::

        >>> Color['BLUE']
        <Color.BLUE: 3>

   .. method:: EnumType.__iter__(cls)

      Returns each member in *cls* in definition order::

        >>> list(Color)
        [<Color.RED: 1>, <Color.GREEN: 2>, <Color.BLUE: 3>]

   .. method:: EnumType.__len__(cls)

      Returns the number of member in *cls*::

        >>> 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>]


.. class:: Enum

   *Enum* is the base class for all *enum* enumerations.

   .. attribute:: Enum.name

      The name used to define the ``Enum`` member::

        >>> Color.BLUE.name
        'BLUE'

   .. attribute:: Enum.value

      The value given to the ``Enum`` member::

         >>> Color.RED.value
         1

      Value of the member, can be set in :meth:`~Enum.__new__`.

      .. note:: Enum member values

         Member values can be anything: :class:`int`, :class:`str`, etc.  If
         the exact value is unimportant you may use :class:`auto` instances and an
         appropriate value will be chosen for you.  See :class:`auto` for the
         details.

         While mutable/unhashable values, such as :class:`dict`, :class:`list` or
         a mutable :class:`~dataclasses.dataclass`, can be used, they will have a
         quadratic performance impact during creation relative to the
         total number of mutable/unhashable values in the enum.

   .. attribute:: Enum._name_

      Name of the member.

   .. attribute:: Enum._value_

      Value of the member, can be set in :meth:`~Enum.__new__`.

   .. attribute:: Enum._order_

      No longer used, kept for backward compatibility.
      (class attribute, removed during class creation).

   .. attribute:: Enum._ignore_

      ``_ignore_`` is only used during creation and is removed from the
      enumeration once creation is complete.

      ``_ignore_`` is a list of names that will not become members, and whose
      names will also be removed from the completed enumeration.  See
      :ref:`TimePeriod <enum-time-period>` for an example.

   .. method:: Enum.__dir__(self)

      Returns ``['__class__', '__doc__', '__module__', 'name', 'value']`` and
      any public methods defined on *self.__class__*::

         >>> from enum import Enum
         >>> from datetime import date
         >>> class Weekday(Enum):
         ...     MONDAY = 1
         ...     TUESDAY = 2
         ...     WEDNESDAY = 3
         ...     THURSDAY = 4
         ...     FRIDAY = 5
         ...     SATURDAY = 6
         ...     SUNDAY = 7
         ...     @classmethod
         ...     def today(cls):
         ...         print('today is %s' % cls(date.today().isoweekday()).name)
         ...
         >>> dir(Weekday.SATURDAY)
         ['__class__', '__doc__', '__eq__', '__hash__', '__module__', 'name', 'today', 'value']

   .. method:: Enum._generate_next_value_(name, start, count, last_values)

         :name: The name of the member being defined (e.g. 'RED').
         :start: The start value for the Enum; the default is 1.
         :count: The number of members currently defined, not including this one.
         :last_values: A list of the previous values.

      A *staticmethod* that is used to determine the next value returned by
      :class:`auto`::

         >>> from enum import auto, Enum
         >>> class PowersOfThree(Enum):
         ...     @staticmethod
         ...     def _generate_next_value_(name, start, count, last_values):
         ...         return 3 ** (count + 1)
         ...     FIRST = auto()
         ...     SECOND = auto()
         ...
         >>> PowersOfThree.SECOND.value
         9

   .. method:: Enum.__init__(self, *args, **kwds)

      By default, does nothing.  If multiple values are given in the member
      assignment, those values become separate arguments to ``__init__``; e.g.

         >>> from enum import Enum
         >>> class Weekday(Enum):
         ...     MONDAY = 1, 'Mon'

      ``Weekday.__init__()`` would be called as ``Weekday.__init__(self, 1, 'Mon')``

   .. method:: Enum.__init_subclass__(cls, **kwds)

      A *classmethod* that is used to further configure subsequent subclasses.
      By default, does nothing.

   .. method:: Enum._missing_(cls, value)

      A *classmethod* for looking up values not found in *cls*.  By default it
      does nothing, but can be overridden to implement custom search behavior::

         >>> from enum import auto, StrEnum
         >>> class Build(StrEnum):
         ...     DEBUG = auto()
         ...     OPTIMIZED = auto()
         ...     @classmethod
         ...     def _missing_(cls, value):
         ...         value = value.lower()
         ...         for member in cls:
         ...             if member.value == value:
         ...                 return member
         ...         return None
         ...
         >>> Build.DEBUG.value
         'debug'
         >>> Build('deBUG')
         <Build.DEBUG: 'debug'>

   .. method:: Enum.__new__(cls, *args, **kwds)

      By default, doesn't exist.  If specified, either in the enum class
      definition or in a mixin class (such as ``int``), all values given
      in the member assignment will be passed; e.g.

         >>> from enum import Enum
         >>> class MyIntEnum(int, Enum):
         ...     TWENTYSIX = '1a', 16

      results in the call ``int('1a', 16)`` and a value of ``26`` for the member.

      .. note::

         When writing a custom ``__new__``, do not use ``super().__new__`` --
         call the appropriate ``__new__`` instead.

   .. method:: Enum.__repr__(self)

      Returns the string used for *repr()* calls.  By default, returns the
      *Enum* name, member name, and value, but can be overridden::

         >>> from enum import auto, Enum
         >>> class OtherStyle(Enum):
         ...     ALTERNATE = auto()
         ...     OTHER = auto()
         ...     SOMETHING_ELSE = auto()
         ...     def __repr__(self):
         ...         cls_name = self.__class__.__name__
         ...         return f'{cls_name}.{self.name}'
         ...
         >>> OtherStyle.ALTERNATE, str(OtherStyle.ALTERNATE), f"{OtherStyle.ALTERNATE}"
         (OtherStyle.ALTERNATE, 'OtherStyle.ALTERNATE', 'OtherStyle.ALTERNATE')

   .. method:: Enum.__str__(self)

      Returns the string used for *str()* calls.  By default, returns the
      *Enum* name and member name, but can be overridden::

         >>> from enum import auto, Enum
         >>> class OtherStyle(Enum):
         ...     ALTERNATE = auto()
         ...     OTHER = auto()
         ...     SOMETHING_ELSE = auto()
         ...     def __str__(self):
         ...         return f'{self.name}'
         ...
         >>> OtherStyle.ALTERNATE, str(OtherStyle.ALTERNATE), f"{OtherStyle.ALTERNATE}"
         (<OtherStyle.ALTERNATE: 1>, 'ALTERNATE', 'ALTERNATE')

   .. method:: Enum.__format__(self)

      Returns the string used for *format()* and *f-string* calls.  By default,
      returns :meth:`__str__` return value, but can be overridden::

         >>> from enum import auto, Enum
         >>> class OtherStyle(Enum):
         ...     ALTERNATE = auto()
         ...     OTHER = auto()
         ...     SOMETHING_ELSE = auto()
         ...     def __format__(self, spec):
         ...         return f'{self.name}'
         ...
         >>> OtherStyle.ALTERNATE, str(OtherStyle.ALTERNATE), f"{OtherStyle.ALTERNATE}"
         (<OtherStyle.ALTERNATE: 1>, 'OtherStyle.ALTERNATE', 'ALTERNATE')

   .. note::

      Using :class:`auto` with :class:`Enum` results in integers of increasing value,
      starting with ``1``.

   .. versionchanged:: 3.12 Added :ref:`enum-dataclass-support`

   .. method:: Enum._add_alias_

      Adds a new name as an alias to an existing member::

         >>> Color.RED._add_alias_("ERROR")
         >>> Color.ERROR
         <Color.RED: 1>

      Raises a :exc:`NameError` if the name is already assigned to a different member.

      .. versionadded:: 3.13

   .. method:: Enum._add_value_alias_

      Adds a new value as an alias to an existing member::

         >>> Color.RED._add_value_alias_(42)
         >>> Color(42)
         <Color.RED: 1>

      Raises a :exc:`ValueError` if the value is already linked with a different member.

      .. versionadded:: 3.13


.. class:: IntEnum

   *IntEnum* is the same as :class:`Enum`, but its members are also integers and can be
   used anywhere that an integer can be used.  If any integer operation is performed
   with an *IntEnum* member, the resulting value loses its enumeration status.

      >>> from enum import IntEnum
      >>> class Number(IntEnum):
      ...     ONE = 1
      ...     TWO = 2
      ...     THREE = 3
      ...
      >>> Number.THREE
      <Number.THREE: 3>
      >>> Number.ONE + Number.TWO
      3
      >>> Number.THREE + 5
      8
      >>> Number.THREE == 3
      True

   .. note::

      Using :class:`auto` with :class:`IntEnum` results in integers of increasing
      value, starting with ``1``.

   .. versionchanged:: 3.11 :meth:`~object.__str__` is now :meth:`!int.__str__` to
      better support the *replacement of existing constants* use-case.
      :meth:`~object.__format__` was already :meth:`!int.__format__` for that same reason.


.. class:: StrEnum

   *StrEnum* is the same as :class:`Enum`, but its members are also strings and
   can be used in most of the same places that a string can be used. The result
   of any string operation performed on or with a *StrEnum* member is not part
   of the enumeration.

   >>> from enum import StrEnum, auto
   >>> class Color(StrEnum):
   ...     RED = 'r'
   ...     GREEN = 'g'
   ...     BLUE = 'b'
   ...     UNKNOWN = auto()
   ...
   >>> Color.RED
   <Color.RED: 'r'>
   >>> Color.UNKNOWN
   <Color.UNKNOWN: 'unknown'>
   >>> str(Color.UNKNOWN)
   'unknown'

   .. note::

      There are places in the stdlib that check for an exact :class:`str`
      instead of a :class:`str` subclass (i.e. ``type(unknown) == str``
      instead of ``isinstance(unknown, str)``), and in those locations you
      will need to use ``str(MyStrEnum.MY_MEMBER)``.

   .. note::

      Using :class:`auto` with :class:`StrEnum` results in the lower-cased member
      name as the value.

   .. note::

      :meth:`~object.__str__` is :meth:`!str.__str__` to better support the
      *replacement of existing constants* use-case.  :meth:`~object.__format__` is likewise
      :meth:`!str.__format__` for that same reason.

   .. versionadded:: 3.11

.. class:: Flag

   ``Flag`` is the same as :class:`Enum`, but its members support the bitwise
   operators ``&`` (*AND*), ``|`` (*OR*), ``^`` (*XOR*), and ``~`` (*INVERT*);
   the results of those operations are (aliases of) members of the enumeration.

   .. method:: __contains__(self, value)

      Returns *True* if value is in self::

         >>> from enum import Flag, auto
         >>> class Color(Flag):
         ...     RED = auto()
         ...     GREEN = auto()
         ...     BLUE = auto()
         ...
         >>> purple = Color.RED | Color.BLUE
         >>> white = Color.RED | Color.GREEN | Color.BLUE
         >>> Color.GREEN in purple
         False
         >>> Color.GREEN in white
         True
         >>> purple in white
         True
         >>> white in purple
         False

   .. method:: __iter__(self):

      Returns all contained non-alias members::

         >>> list(Color.RED)
         [<Color.RED: 1>]
         >>> list(purple)
         [<Color.RED: 1>, <Color.BLUE: 4>]

      .. versionadded:: 3.11

   .. method:: __len__(self):

      Returns number of members in flag::

         >>> len(Color.GREEN)
         1
         >>> len(white)
         3

      .. versionadded:: 3.11

   .. method:: __bool__(self):

      Returns *True* if any members in flag, *False* otherwise::

         >>> bool(Color.GREEN)
         True
         >>> bool(white)
         True
         >>> black = Color(0)
         >>> bool(black)
         False

   .. method:: __or__(self, other)

      Returns current flag binary or'ed with other::

         >>> Color.RED | Color.GREEN
         <Color.RED|GREEN: 3>

   .. method:: __and__(self, other)

      Returns current flag binary and'ed with other::

         >>> purple & white
         <Color.RED|BLUE: 5>
         >>> purple & Color.GREEN
         <Color: 0>

   .. method:: __xor__(self, other)

      Returns current flag binary xor'ed with other::

         >>> purple ^ white
         <Color.GREEN: 2>
         >>> purple ^ Color.GREEN
         <Color.RED|GREEN|BLUE: 7>

   .. method:: __invert__(self):

      Returns all the flags in *type(self)* that are not in *self*::

         >>> ~white
         <Color: 0>
         >>> ~purple
         <Color.GREEN: 2>
         >>> ~Color.RED
         <Color.GREEN|BLUE: 6>

   .. method:: _numeric_repr_

      Function used to format any remaining unnamed numeric values.  Default is
      the value's repr; common choices are :func:`hex` and :func:`oct`.

   .. note::

      Using :class:`auto` with :class:`Flag` results in integers that are powers
      of two, starting with ``1``.

   .. versionchanged:: 3.11 The *repr()* of zero-valued flags has changed.  It
      is now:

         >>> Color(0) # doctest: +SKIP
         <Color: 0>

.. class:: IntFlag

   ``IntFlag`` is the same as :class:`Flag`, but its members are also integers and can be
   used anywhere that an integer can be used.

      >>> from enum import IntFlag, auto
      >>> class Color(IntFlag):
      ...     RED = auto()
      ...     GREEN = auto()
      ...     BLUE = auto()
      ...
      >>> Color.RED & 2
      <Color: 0>
      >>> Color.RED | 2
      <Color.RED|GREEN: 3>

   If any integer operation is performed with an *IntFlag* member, the result is
   not an *IntFlag*::

        >>> Color.RED + 2
        3

   If a :class:`Flag` operation is performed with an *IntFlag* member and:

   * the result is a valid *IntFlag*: an *IntFlag* is returned
   * the result is not a valid *IntFlag*: the result depends on the :class:`FlagBoundary` setting

   The :func:`repr` of unnamed zero-valued flags has changed.  It is now::

      >>> Color(0)
      <Color: 0>

   .. note::

      Using :class:`auto` with :class:`IntFlag` results in integers that are powers
      of two, starting with ``1``.

   .. versionchanged:: 3.11

      :meth:`~object.__str__` is now :meth:`!int.__str__` to better support the
      *replacement of existing constants* use-case.  :meth:`~object.__format__` was
      already :meth:`!int.__format__` for that same reason.

      Inversion of an :class:`!IntFlag` now returns a positive value that is the
      union of all flags not in the given flag, rather than a negative value.
      This matches the existing :class:`Flag` behavior.

.. class:: ReprEnum

   :class:`!ReprEnum` uses the :meth:`repr() <Enum.__repr__>` of :class:`Enum`,
   but the :class:`str() <str>` of the mixed-in data type:

   * :meth:`!int.__str__` for :class:`IntEnum` and :class:`IntFlag`
   * :meth:`!str.__str__` for :class:`StrEnum`

   Inherit from :class:`!ReprEnum` to keep the :class:`str() <str>` / :func:`format`
   of the mixed-in data type instead of using the
   :class:`Enum`-default :meth:`str() <Enum.__str__>`.


   .. versionadded:: 3.11

.. class:: EnumCheck

   *EnumCheck* contains the options used by the :func:`verify` decorator to ensure
   various constraints; failed constraints result in a :exc:`ValueError`.

   .. attribute:: UNIQUE

      Ensure that each value has only one name::

         >>> from enum import Enum, verify, UNIQUE
         >>> @verify(UNIQUE)
         ... class Color(Enum):
         ...     RED = 1
         ...     GREEN = 2
         ...     BLUE = 3
         ...     CRIMSON = 1
         Traceback (most recent call last):
         ...
         ValueError: aliases found in <enum 'Color'>: CRIMSON -> RED


   .. attribute:: CONTINUOUS

      Ensure that there are no missing values between the lowest-valued member
      and the highest-valued member::

         >>> from enum import Enum, verify, CONTINUOUS
         >>> @verify(CONTINUOUS)
         ... class Color(Enum):
         ...     RED = 1
         ...     GREEN = 2
         ...     BLUE = 5
         Traceback (most recent call last):
         ...
         ValueError: invalid enum 'Color': missing values 3, 4

   .. attribute:: NAMED_FLAGS

      Ensure that any flag groups/masks contain only named flags -- useful when
      values are specified instead of being generated by :func:`auto`::

         >>> from enum import Flag, verify, NAMED_FLAGS
         >>> @verify(NAMED_FLAGS)
         ... class Color(Flag):
         ...     RED = 1
         ...     GREEN = 2
         ...     BLUE = 4
         ...     WHITE = 15
         ...     NEON = 31
         Traceback (most recent call last):
         ...
         ValueError: invalid Flag 'Color': aliases WHITE and NEON are missing combined values of 0x18 [use enum.show_flag_values(value) for details]

   .. note::

      CONTINUOUS and NAMED_FLAGS are designed to work with integer-valued members.

   .. versionadded:: 3.11

.. class:: FlagBoundary

   ``FlagBoundary`` controls how out-of-range values are handled in :class:`Flag` and its
   subclasses.

   .. attribute:: STRICT

      Out-of-range values cause a :exc:`ValueError` to be raised. This is the
      default for :class:`Flag`::

         >>> from enum import Flag, STRICT, auto
         >>> class StrictFlag(Flag, boundary=STRICT):
         ...     RED = auto()
         ...     GREEN = auto()
         ...     BLUE = auto()
         ...
         >>> StrictFlag(2**2 + 2**4)
         Traceback (most recent call last):
         ...
         ValueError: <flag 'StrictFlag'> invalid value 20
             given 0b0 10100
           allowed 0b0 00111

   .. attribute:: CONFORM

      Out-of-range values have invalid values removed, leaving a valid :class:`Flag`
      value::

         >>> from enum import Flag, CONFORM, auto
         >>> class ConformFlag(Flag, boundary=CONFORM):
         ...     RED = auto()
         ...     GREEN = auto()
         ...     BLUE = auto()
         ...
         >>> ConformFlag(2**2 + 2**4)
         <ConformFlag.BLUE: 4>

   .. attribute:: EJECT

      Out-of-range values lose their :class:`Flag` membership and revert to :class:`int`.

         >>> from enum import Flag, EJECT, auto
         >>> class EjectFlag(Flag, boundary=EJECT):
         ...     RED = auto()
         ...     GREEN = auto()
         ...     BLUE = auto()
         ...
         >>> EjectFlag(2**2 + 2**4)
         20

   .. attribute:: KEEP

      Out-of-range values are kept, and the :class:`Flag` membership is kept.
      This is the default for :class:`IntFlag`::

         >>> from enum import Flag, KEEP, auto
         >>> class KeepFlag(Flag, boundary=KEEP):
         ...     RED = auto()
         ...     GREEN = auto()
         ...     BLUE = auto()
         ...
         >>> KeepFlag(2**2 + 2**4)
         <KeepFlag.BLUE|16: 20>

   .. versionadded:: 3.11

.. class:: EnumDict

   *EnumDict* is a subclass of :class:`dict` that is used as the namespace
   for defining enum classes (see :ref:`prepare`).
   It is exposed to allow subclasses of :class:`EnumType` with advanced
   behavior like having multiple values per member.
   It should be called with the name of the enum class being created, otherwise
   private names and internal classes will not be handled correctly.

   Note that only the :class:`~collections.abc.MutableMapping` interface
   (:meth:`~object.__setitem__` and :meth:`~dict.update`) is overridden.
   It may be possible to bypass the checks using other :class:`!dict`
   operations like :meth:`|= <object.__ior__>`.

   .. attribute:: EnumDict.member_names

      A list of member names.

   .. versionadded:: 3.13

---------------

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:`~Enum.__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
""""""""""""""""""""""""""""

- :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_` -- no longer used, kept for backward
  compatibility (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.

- :meth:`~Enum._add_alias_` -- adds a new name as an alias to an existing
  member.
- :meth:`~Enum._add_value_alias_` -- adds a new value as an alias to an
  existing member.

- While ``_sunder_`` names are generally reserved for the further development
  of the :class:`Enum` class and can not be used, some are explicitly allowed:

  - ``_repr_*`` (e.g. ``_repr_html_``), as used in `IPython's rich display`_

.. versionadded:: 3.6 ``_missing_``, ``_order_``, ``_generate_next_value_``
.. versionadded:: 3.7 ``_ignore_``
.. versionadded:: 3.13 ``_add_alias_``, ``_add_value_alias_``, ``_repr_*``
.. _`IPython's rich display`: https://ipython.readthedocs.io/en/stable/config/integrating.html#rich-display

---------------

Utilities and Decorators
------------------------

.. class:: auto

   *auto* can be used in place of a value.  If used, the *Enum* machinery will
   call an :class:`Enum`'s :meth:`~Enum._generate_next_value_` to get an appropriate value.
   For :class:`Enum` and :class:`IntEnum` that appropriate value will be the last value plus
   one; for :class:`Flag` and :class:`IntFlag` it will be the first power-of-two greater
   than the highest value; for :class:`StrEnum` it will be the lower-cased version of
   the member's name.  Care must be taken if mixing *auto()* with manually
   specified values.

   *auto* instances are only resolved when at the top level of an assignment, either by
   itself or as part of a tuple:

   * ``FIRST = auto()`` will work (auto() is replaced with ``1``);
   * ``SECOND = auto(), -2`` will work (auto is replaced with ``2``, so ``2, -2`` is
     used to create the ``SECOND`` enum member;
   * ``THREE = [auto(), -3]`` will *not* work (``[<auto instance>, -3]`` is used to
     create the ``THREE`` enum member)

   .. versionchanged:: 3.11.1

      In prior versions, ``auto()`` had to be the only thing
      on the assignment line to work properly.

   ``_generate_next_value_`` can be overridden to customize the values used by
   *auto*.

   .. note:: in 3.13 the default ``_generate_next_value_`` will always return
             the highest member value incremented by 1, and will fail if any
             member is an incompatible type.

.. decorator:: property

   A decorator similar to the built-in *property*, but specifically for
   enumerations.  It allows member attributes to have the same names as members
   themselves.

   .. note:: the *property* and the member must be defined in separate classes;
             for example, the *value* and *name* attributes are defined in the
             *Enum* class, and *Enum* subclasses can define members with the
             names ``value`` and ``name``.

   .. versionadded:: 3.11

.. decorator:: unique

   A :keyword:`class` decorator specifically for enumerations.  It searches an
   enumeration's :attr:`~EnumType.__members__`, gathering any aliases it finds; if any are
   found :exc:`ValueError` is raised with the details::

      >>> from enum import Enum, unique
      >>> @unique
      ... class Mistake(Enum):
      ...     ONE = 1
      ...     TWO = 2
      ...     THREE = 3
      ...     FOUR = 3
      ...
      Traceback (most recent call last):
      ...
      ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE

.. decorator:: verify

   A :keyword:`class` decorator specifically for enumerations.  Members from
   :class:`EnumCheck` are used to specify which constraints should be checked
   on the decorated enumeration.

   .. versionadded:: 3.11

.. decorator:: member

   A decorator for use in enums: its target will become a member.

   .. versionadded:: 3.11

.. decorator:: nonmember

   A decorator for use in enums: its target will not become a member.

   .. versionadded:: 3.11

.. decorator:: global_enum

   A decorator to change the :class:`str() <str>` and :func:`repr` of an enum
   to show its members as belonging to the module instead of its class.
   Should only be used when the enum members are exported
   to the module global namespace (see :class:`re.RegexFlag` for an example).


   .. versionadded:: 3.11

.. function:: show_flag_values(value)

   Return a list of all power-of-two integers contained in a flag *value*.

   .. versionadded:: 3.11

---------------

Notes
-----

:class:`IntEnum`, :class:`StrEnum`, and :class:`IntFlag`

   These three enum types are designed to be drop-in replacements for existing
   integer- and string-based values; as such, they have extra limitations:

   - ``__str__`` uses the value and not the name of the enum member

   - ``__format__``, because it uses ``__str__``, will also use the value of
     the enum member instead of its name

   If you do not need/want those limitations, you can either create your own
   base class by mixing in the ``int`` or ``str`` type yourself::

       >>> from enum import Enum
       >>> class MyIntEnum(int, Enum):
       ...     pass

   or you can reassign the appropriate :meth:`str`, etc., in your enum::

       >>> from enum import Enum, IntEnum
       >>> class MyIntEnum(IntEnum):
       ...     __str__ = Enum.__str__