enum.rst

: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`

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', 'GREEN', 'BLUE'])

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:`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``

---

Data Types

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.

.. 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>]

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

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

   .. 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.

.. attribute:: Enum._name_

   Name of the member.

.. attribute:: Enum._value_

   Value of the member, can be set in :meth:`~object.__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 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
      >>> 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 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(Enum):
      ...     SEVENTEEN = '1a', 16

   results in the call ``int('1a', 16)`` and a value of ``17`` for the member.

.. 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::

      >>> 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::

      >>> 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::

      >>> 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`

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.

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.

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(StrEnum.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

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

.. 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>

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` 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

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

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

---

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.

Supported _sunder_ names

• :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_` -- 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.

.. versionadded:: 3.6 ``_missing_``, ``_order_``, ``_generate_next_value_``

.. versionadded:: 3.7 ``_ignore_``

.. versionadded:: 3.13 ``_add_alias_``, ``_add_value_alias_``

---

Utilities and Decorators

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:

• 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__