summaryrefslogtreecommitdiffstats
path: root/Doc/library/enum.rst
blob: e9c4f0e2c5f59b2f495551aa62607678245477cf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
: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', '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
----------


.. 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.

   .. 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

      .. note::

         In Python 3.12 it will be possible to check for member values and not
         just members; until then, a ``TypeError`` will be 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

   .. 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

      .. 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._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_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.__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`


.. class:: IntEnum

   *IntEnum* is the same as *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 *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

.. class:: Flag

   *Flag* 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>]

      .. versionchanged:: 3.11

         Aliases are no longer returned during iteration.

   .. 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>

.. class:: IntFlag

   *IntFlag* is the same as *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 *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 *FlagBoundary* setting

   The *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 *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 *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 *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 *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
""""""""""""""""""""""""""""

- ``_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

   .. 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.

.. versionadded:: 3.6 ``_missing_``, ``_order_``, ``_generate_next_value_``
.. versionadded:: 3.7 ``_ignore_``

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

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

.. class:: auto

   *auto* can be used in place of a value.  If used, the *Enum* machinery will
   call an *Enum*'s :meth:`~Enum._generate_next_value_` to get an appropriate value.
   For *Enum* and *IntEnum* that appropriate value will be the last value plus
   one; for *Flag* and *IntFlag* it will be the first power-of-two greater
   than the highest value; for *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__