Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 1 | :mod:`enum` --- Support for enumerations |
| 2 | ======================================== |
| 3 | |
| 4 | .. module:: enum |
Brett Cannon | 15e489f | 2013-06-14 21:59:16 -0400 | [diff] [blame] | 5 | :synopsis: Implementation of an enumeration class. |
| 6 | |
Andrés Delfino | 2d74838 | 2018-07-07 16:01:25 -0300 | [diff] [blame] | 7 | .. moduleauthor:: Ethan Furman <ethan@stoneleaf.us> |
| 8 | .. sectionauthor:: Barry Warsaw <barry@python.org> |
| 9 | .. sectionauthor:: Eli Bendersky <eliben@gmail.com> |
| 10 | .. sectionauthor:: Ethan Furman <ethan@stoneleaf.us> |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 11 | |
R David Murray | fd1ff1c | 2013-12-20 14:20:49 -0500 | [diff] [blame] | 12 | .. versionadded:: 3.4 |
| 13 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 14 | **Source code:** :source:`Lib/enum.py` |
| 15 | |
| 16 | ---------------- |
| 17 | |
Ethan Furman | c72e638 | 2014-02-06 08:13:14 -0800 | [diff] [blame] | 18 | An enumeration is a set of symbolic names (members) bound to unique, |
| 19 | constant values. Within an enumeration, the members can be compared |
| 20 | by identity, and the enumeration itself can be iterated over. |
| 21 | |
Ethan Furman | 542e1df | 2020-09-14 13:32:44 -0700 | [diff] [blame] | 22 | .. note:: Case of Enum Members |
| 23 | |
| 24 | Because Enums are used to represent constants we recommend using |
| 25 | UPPER_CASE names for enum members, and will be using that style |
| 26 | in our examples. |
| 27 | |
Ethan Furman | c72e638 | 2014-02-06 08:13:14 -0800 | [diff] [blame] | 28 | |
| 29 | Module Contents |
| 30 | --------------- |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 31 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 32 | This module defines four enumeration classes that can be used to define unique |
Kartik Anand | 6265842 | 2017-03-01 01:37:19 +0530 | [diff] [blame] | 33 | sets of names and values: :class:`Enum`, :class:`IntEnum`, :class:`Flag`, and |
| 34 | :class:`IntFlag`. It also defines one decorator, :func:`unique`, and one |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 35 | helper, :class:`auto`. |
Ethan Furman | c72e638 | 2014-02-06 08:13:14 -0800 | [diff] [blame] | 36 | |
| 37 | .. class:: Enum |
| 38 | |
| 39 | Base class for creating enumerated constants. See section |
Larry Hastings | ad88d7a | 2014-02-10 04:26:10 -0800 | [diff] [blame] | 40 | `Functional API`_ for an alternate construction syntax. |
Ethan Furman | c72e638 | 2014-02-06 08:13:14 -0800 | [diff] [blame] | 41 | |
| 42 | .. class:: IntEnum |
| 43 | |
| 44 | Base class for creating enumerated constants that are also |
| 45 | subclasses of :class:`int`. |
| 46 | |
Ethan Furman | 0063ff4 | 2020-09-21 17:23:13 -0700 | [diff] [blame] | 47 | .. class:: StrEnum |
| 48 | |
| 49 | Base class for creating enumerated constants that are also |
| 50 | subclasses of :class:`str`. |
| 51 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 52 | .. class:: IntFlag |
| 53 | |
| 54 | Base class for creating enumerated constants that can be combined using |
| 55 | the bitwise operators without losing their :class:`IntFlag` membership. |
| 56 | :class:`IntFlag` members are also subclasses of :class:`int`. |
| 57 | |
| 58 | .. class:: Flag |
| 59 | |
| 60 | Base class for creating enumerated constants that can be combined using |
| 61 | the bitwise operations without losing their :class:`Flag` membership. |
| 62 | |
Ethan Furman | c72e638 | 2014-02-06 08:13:14 -0800 | [diff] [blame] | 63 | .. function:: unique |
Victor Stinner | d3ded08 | 2020-08-13 21:41:54 +0200 | [diff] [blame] | 64 | :noindex: |
Ethan Furman | c72e638 | 2014-02-06 08:13:14 -0800 | [diff] [blame] | 65 | |
| 66 | Enum class decorator that ensures only one name is bound to any one value. |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 67 | |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 68 | .. class:: auto |
| 69 | |
YoSTEALTH | 24bcefc | 2020-01-06 16:04:43 -0600 | [diff] [blame] | 70 | Instances are replaced with an appropriate value for Enum members. By default, the initial value starts at 1. |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 71 | |
| 72 | .. versionadded:: 3.6 ``Flag``, ``IntFlag``, ``auto`` |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 73 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 74 | |
| 75 | Creating an Enum |
| 76 | ---------------- |
| 77 | |
| 78 | Enumerations are created using the :keyword:`class` syntax, which makes them |
| 79 | easy to read and write. An alternative creation method is described in |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 80 | `Functional API`_. To define an enumeration, subclass :class:`Enum` as |
| 81 | follows:: |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 82 | |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 83 | >>> from enum import Enum |
| 84 | >>> class Color(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 85 | ... RED = 1 |
| 86 | ... GREEN = 2 |
| 87 | ... BLUE = 3 |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 88 | ... |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 89 | |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 90 | .. note:: Enum member values |
| 91 | |
| 92 | Member values can be anything: :class:`int`, :class:`str`, etc.. If |
| 93 | the exact value is unimportant you may use :class:`auto` instances and an |
| 94 | appropriate value will be chosen for you. Care must be taken if you mix |
| 95 | :class:`auto` with other values. |
| 96 | |
Ethan Furman | 455bfde | 2013-09-08 23:48:34 -0700 | [diff] [blame] | 97 | .. note:: Nomenclature |
| 98 | |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 99 | - The class :class:`Color` is an *enumeration* (or *enum*) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 100 | - The attributes :attr:`Color.RED`, :attr:`Color.GREEN`, etc., are |
| 101 | *enumeration members* (or *enum members*) and are functionally constants. |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 102 | - The enum members have *names* and *values* (the name of |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 103 | :attr:`Color.RED` is ``RED``, the value of :attr:`Color.BLUE` is |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 104 | ``3``, etc.) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 105 | |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 106 | .. note:: |
| 107 | |
| 108 | Even though we use the :keyword:`class` syntax to create Enums, Enums |
| 109 | are not normal Python classes. See `How are Enums different?`_ for |
| 110 | more details. |
| 111 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 112 | Enumeration members have human readable string representations:: |
| 113 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 114 | >>> print(Color.RED) |
| 115 | Color.RED |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 116 | |
| 117 | ...while their ``repr`` has more information:: |
| 118 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 119 | >>> print(repr(Color.RED)) |
| 120 | <Color.RED: 1> |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 121 | |
| 122 | The *type* of an enumeration member is the enumeration it belongs to:: |
| 123 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 124 | >>> type(Color.RED) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 125 | <enum 'Color'> |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 126 | >>> isinstance(Color.GREEN, Color) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 127 | True |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 128 | |
| 129 | Enum members also have a property that contains just their item name:: |
| 130 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 131 | >>> print(Color.RED.name) |
| 132 | RED |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 133 | |
| 134 | Enumerations support iteration, in definition order:: |
| 135 | |
| 136 | >>> class Shake(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 137 | ... VANILLA = 7 |
| 138 | ... CHOCOLATE = 4 |
| 139 | ... COOKIES = 9 |
| 140 | ... MINT = 3 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 141 | ... |
| 142 | >>> for shake in Shake: |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 143 | ... print(shake) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 144 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 145 | Shake.VANILLA |
| 146 | Shake.CHOCOLATE |
| 147 | Shake.COOKIES |
| 148 | Shake.MINT |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 149 | |
| 150 | Enumeration members are hashable, so they can be used in dictionaries and sets:: |
| 151 | |
| 152 | >>> apples = {} |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 153 | >>> apples[Color.RED] = 'red delicious' |
| 154 | >>> apples[Color.GREEN] = 'granny smith' |
| 155 | >>> apples == {Color.RED: 'red delicious', Color.GREEN: 'granny smith'} |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 156 | True |
| 157 | |
| 158 | |
Ethan Furman | 3fe70b4a | 2013-06-28 14:02:34 -0700 | [diff] [blame] | 159 | Programmatic access to enumeration members and their attributes |
| 160 | --------------------------------------------------------------- |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 161 | |
| 162 | Sometimes it's useful to access members in enumerations programmatically (i.e. |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 163 | situations where ``Color.RED`` won't do because the exact color is not known |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 164 | at program-writing time). ``Enum`` allows such access:: |
| 165 | |
| 166 | >>> Color(1) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 167 | <Color.RED: 1> |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 168 | >>> Color(3) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 169 | <Color.BLUE: 3> |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 170 | |
| 171 | If you want to access enum members by *name*, use item access:: |
| 172 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 173 | >>> Color['RED'] |
| 174 | <Color.RED: 1> |
| 175 | >>> Color['GREEN'] |
| 176 | <Color.GREEN: 2> |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 177 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 178 | If you have an enum member and need its :attr:`name` or :attr:`value`:: |
Ethan Furman | 3fe70b4a | 2013-06-28 14:02:34 -0700 | [diff] [blame] | 179 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 180 | >>> member = Color.RED |
Ethan Furman | 3fe70b4a | 2013-06-28 14:02:34 -0700 | [diff] [blame] | 181 | >>> member.name |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 182 | 'RED' |
Ethan Furman | 3fe70b4a | 2013-06-28 14:02:34 -0700 | [diff] [blame] | 183 | >>> member.value |
| 184 | 1 |
| 185 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 186 | |
| 187 | Duplicating enum members and values |
| 188 | ----------------------------------- |
| 189 | |
| 190 | Having two enum members with the same name is invalid:: |
| 191 | |
| 192 | >>> class Shape(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 193 | ... SQUARE = 2 |
| 194 | ... SQUARE = 3 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 195 | ... |
| 196 | Traceback (most recent call last): |
| 197 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 198 | TypeError: Attempted to reuse key: 'SQUARE' |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 199 | |
| 200 | However, two enum members are allowed to have the same value. Given two members |
| 201 | A and B with the same value (and A defined first), B is an alias to A. By-value |
| 202 | lookup of the value of A and B will return A. By-name lookup of B will also |
| 203 | return A:: |
| 204 | |
| 205 | >>> class Shape(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 206 | ... SQUARE = 2 |
| 207 | ... DIAMOND = 1 |
| 208 | ... CIRCLE = 3 |
| 209 | ... ALIAS_FOR_SQUARE = 2 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 210 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 211 | >>> Shape.SQUARE |
| 212 | <Shape.SQUARE: 2> |
| 213 | >>> Shape.ALIAS_FOR_SQUARE |
| 214 | <Shape.SQUARE: 2> |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 215 | >>> Shape(2) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 216 | <Shape.SQUARE: 2> |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 217 | |
Ethan Furman | 101e074 | 2013-09-15 12:34:36 -0700 | [diff] [blame] | 218 | .. note:: |
| 219 | |
| 220 | Attempting to create a member with the same name as an already |
| 221 | defined attribute (another member, a method, etc.) or attempting to create |
| 222 | an attribute with the same name as a member is not allowed. |
| 223 | |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 224 | |
| 225 | Ensuring unique enumeration values |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 226 | ---------------------------------- |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 227 | |
| 228 | By default, enumerations allow multiple names as aliases for the same value. |
| 229 | When this behavior isn't desired, the following decorator can be used to |
| 230 | ensure each value is used only once in the enumeration: |
| 231 | |
| 232 | .. decorator:: unique |
| 233 | |
| 234 | A :keyword:`class` decorator specifically for enumerations. It searches an |
| 235 | enumeration's :attr:`__members__` gathering any aliases it finds; if any are |
| 236 | found :exc:`ValueError` is raised with the details:: |
| 237 | |
| 238 | >>> from enum import Enum, unique |
| 239 | >>> @unique |
| 240 | ... class Mistake(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 241 | ... ONE = 1 |
| 242 | ... TWO = 2 |
| 243 | ... THREE = 3 |
| 244 | ... FOUR = 3 |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 245 | ... |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 246 | Traceback (most recent call last): |
| 247 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 248 | ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 249 | |
| 250 | |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 251 | Using automatic values |
| 252 | ---------------------- |
| 253 | |
| 254 | If the exact value is unimportant you can use :class:`auto`:: |
| 255 | |
| 256 | >>> from enum import Enum, auto |
| 257 | >>> class Color(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 258 | ... RED = auto() |
| 259 | ... BLUE = auto() |
| 260 | ... GREEN = auto() |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 261 | ... |
| 262 | >>> list(Color) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 263 | [<Color.RED: 1>, <Color.BLUE: 2>, <Color.GREEN: 3>] |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 264 | |
| 265 | The values are chosen by :func:`_generate_next_value_`, which can be |
| 266 | overridden:: |
| 267 | |
| 268 | >>> class AutoName(Enum): |
| 269 | ... def _generate_next_value_(name, start, count, last_values): |
| 270 | ... return name |
| 271 | ... |
| 272 | >>> class Ordinal(AutoName): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 273 | ... NORTH = auto() |
| 274 | ... SOUTH = auto() |
| 275 | ... EAST = auto() |
| 276 | ... WEST = auto() |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 277 | ... |
| 278 | >>> list(Ordinal) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 279 | [<Ordinal.NORTH: 'NORTH'>, <Ordinal.SOUTH: 'SOUTH'>, <Ordinal.EAST: 'EAST'>, <Ordinal.WEST: 'WEST'>] |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 280 | |
| 281 | .. note:: |
| 282 | |
| 283 | The goal of the default :meth:`_generate_next_value_` methods is to provide |
| 284 | the next :class:`int` in sequence with the last :class:`int` provided, but |
| 285 | the way it does this is an implementation detail and may change. |
| 286 | |
Ethan Onstott | d9a43e2 | 2020-04-28 13:20:55 -0400 | [diff] [blame] | 287 | .. note:: |
| 288 | |
| 289 | The :meth:`_generate_next_value_` method must be defined before any members. |
| 290 | |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 291 | Iteration |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 292 | --------- |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 293 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 294 | Iterating over the members of an enum does not provide the aliases:: |
| 295 | |
| 296 | >>> list(Shape) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 297 | [<Shape.SQUARE: 2>, <Shape.DIAMOND: 1>, <Shape.CIRCLE: 3>] |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 298 | |
INADA Naoki | e57f91a | 2018-06-19 01:14:26 +0900 | [diff] [blame] | 299 | The special attribute ``__members__`` is a read-only ordered mapping of names |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 300 | to members. It includes all names defined in the enumeration, including the |
| 301 | aliases:: |
| 302 | |
| 303 | >>> for name, member in Shape.__members__.items(): |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 304 | ... name, member |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 305 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 306 | ('SQUARE', <Shape.SQUARE: 2>) |
| 307 | ('DIAMOND', <Shape.DIAMOND: 1>) |
| 308 | ('CIRCLE', <Shape.CIRCLE: 3>) |
| 309 | ('ALIAS_FOR_SQUARE', <Shape.SQUARE: 2>) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 310 | |
| 311 | The ``__members__`` attribute can be used for detailed programmatic access to |
| 312 | the enumeration members. For example, finding all the aliases:: |
| 313 | |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 314 | >>> [name for name, member in Shape.__members__.items() if member.name != name] |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 315 | ['ALIAS_FOR_SQUARE'] |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 316 | |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 317 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 318 | Comparisons |
| 319 | ----------- |
| 320 | |
| 321 | Enumeration members are compared by identity:: |
| 322 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 323 | >>> Color.RED is Color.RED |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 324 | True |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 325 | >>> Color.RED is Color.BLUE |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 326 | False |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 327 | >>> Color.RED is not Color.BLUE |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 328 | True |
| 329 | |
| 330 | Ordered comparisons between enumeration values are *not* supported. Enum |
| 331 | members are not integers (but see `IntEnum`_ below):: |
| 332 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 333 | >>> Color.RED < Color.BLUE |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 334 | Traceback (most recent call last): |
| 335 | File "<stdin>", line 1, in <module> |
Ethan Furman | e8e6127 | 2016-08-20 07:19:31 -0700 | [diff] [blame] | 336 | TypeError: '<' not supported between instances of 'Color' and 'Color' |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 337 | |
| 338 | Equality comparisons are defined though:: |
| 339 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 340 | >>> Color.BLUE == Color.RED |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 341 | False |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 342 | >>> Color.BLUE != Color.RED |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 343 | True |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 344 | >>> Color.BLUE == Color.BLUE |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 345 | True |
| 346 | |
| 347 | Comparisons against non-enumeration values will always compare not equal |
Ezio Melotti | 93d7dda | 2013-10-05 04:13:18 +0300 | [diff] [blame] | 348 | (again, :class:`IntEnum` was explicitly designed to behave differently, see |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 349 | below):: |
| 350 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 351 | >>> Color.BLUE == 2 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 352 | False |
| 353 | |
| 354 | |
| 355 | Allowed members and attributes of enumerations |
| 356 | ---------------------------------------------- |
| 357 | |
| 358 | The examples above use integers for enumeration values. Using integers is |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 359 | short and handy (and provided by default by the `Functional API`_), but not |
| 360 | strictly enforced. In the vast majority of use-cases, one doesn't care what |
| 361 | the actual value of an enumeration is. But if the value *is* important, |
| 362 | enumerations can have arbitrary values. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 363 | |
| 364 | Enumerations are Python classes, and can have methods and special methods as |
| 365 | usual. If we have this enumeration:: |
| 366 | |
| 367 | >>> class Mood(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 368 | ... FUNKY = 1 |
| 369 | ... HAPPY = 3 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 370 | ... |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 371 | ... def describe(self): |
| 372 | ... # self is the member here |
| 373 | ... return self.name, self.value |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 374 | ... |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 375 | ... def __str__(self): |
| 376 | ... return 'my custom str! {0}'.format(self.value) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 377 | ... |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 378 | ... @classmethod |
| 379 | ... def favorite_mood(cls): |
| 380 | ... # cls here is the enumeration |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 381 | ... return cls.HAPPY |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 382 | ... |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 383 | |
| 384 | Then:: |
| 385 | |
| 386 | >>> Mood.favorite_mood() |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 387 | <Mood.HAPPY: 3> |
| 388 | >>> Mood.HAPPY.describe() |
| 389 | ('HAPPY', 3) |
| 390 | >>> str(Mood.FUNKY) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 391 | 'my custom str! 1' |
| 392 | |
Martin Panter | a90a4a9 | 2016-05-30 04:04:50 +0000 | [diff] [blame] | 393 | The rules for what is allowed are as follows: names that start and end with |
| 394 | a single underscore are reserved by enum and cannot be used; all other |
Ethan Furman | 8be6fac | 2014-11-01 07:40:22 -0700 | [diff] [blame] | 395 | attributes defined within an enumeration will become members of this |
| 396 | enumeration, with the exception of special methods (:meth:`__str__`, |
Ethan Furman | a4b1bb4 | 2018-01-22 07:56:37 -0800 | [diff] [blame] | 397 | :meth:`__add__`, etc.), descriptors (methods are also descriptors), and |
| 398 | variable names listed in :attr:`_ignore_`. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 399 | |
| 400 | Note: if your enumeration defines :meth:`__new__` and/or :meth:`__init__` then |
Antoine | d3c8d73 | 2019-08-20 03:41:31 +0200 | [diff] [blame] | 401 | any value(s) given to the enum member will be passed into those methods. |
| 402 | See `Planet`_ for an example. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 403 | |
| 404 | |
Ethan Furman | 5bdab64 | 2018-09-21 19:03:09 -0700 | [diff] [blame] | 405 | Restricted Enum subclassing |
| 406 | --------------------------- |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 407 | |
Ethan Furman | 5bdab64 | 2018-09-21 19:03:09 -0700 | [diff] [blame] | 408 | A new :class:`Enum` class must have one base Enum class, up to one concrete |
| 409 | data type, and as many :class:`object`-based mixin classes as needed. The |
| 410 | order of these base classes is:: |
| 411 | |
nu_no | dfc8bb9 | 2019-01-27 23:07:47 +0100 | [diff] [blame] | 412 | class EnumName([mix-in, ...,] [data-type,] base-enum): |
Ethan Furman | 5bdab64 | 2018-09-21 19:03:09 -0700 | [diff] [blame] | 413 | pass |
| 414 | |
| 415 | Also, subclassing an enumeration is allowed only if the enumeration does not define |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 416 | any members. So this is forbidden:: |
| 417 | |
| 418 | >>> class MoreColor(Color): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 419 | ... PINK = 17 |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 420 | ... |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 421 | Traceback (most recent call last): |
| 422 | ... |
| 423 | TypeError: Cannot extend enumerations |
| 424 | |
| 425 | But this is allowed:: |
| 426 | |
| 427 | >>> class Foo(Enum): |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 428 | ... def some_behavior(self): |
| 429 | ... pass |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 430 | ... |
| 431 | >>> class Bar(Foo): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 432 | ... HAPPY = 1 |
| 433 | ... SAD = 2 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 434 | ... |
| 435 | |
| 436 | Allowing subclassing of enums that define members would lead to a violation of |
| 437 | some important invariants of types and instances. On the other hand, it makes |
| 438 | sense to allow sharing some common behavior between a group of enumerations. |
| 439 | (See `OrderedEnum`_ for an example.) |
| 440 | |
| 441 | |
| 442 | Pickling |
| 443 | -------- |
| 444 | |
| 445 | Enumerations can be pickled and unpickled:: |
| 446 | |
| 447 | >>> from test.test_enum import Fruit |
| 448 | >>> from pickle import dumps, loads |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 449 | >>> Fruit.TOMATO is loads(dumps(Fruit.TOMATO)) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 450 | True |
| 451 | |
| 452 | The usual restrictions for pickling apply: picklable enums must be defined in |
| 453 | the top level of a module, since unpickling requires them to be importable |
| 454 | from that module. |
| 455 | |
Ethan Furman | ca1b794 | 2014-02-08 11:36:27 -0800 | [diff] [blame] | 456 | .. note:: |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 457 | |
Ethan Furman | ca1b794 | 2014-02-08 11:36:27 -0800 | [diff] [blame] | 458 | With pickle protocol version 4 it is possible to easily pickle enums |
| 459 | nested in other classes. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 460 | |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 461 | It is possible to modify how Enum members are pickled/unpickled by defining |
| 462 | :meth:`__reduce_ex__` in the enumeration class. |
| 463 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 464 | |
| 465 | Functional API |
| 466 | -------------- |
| 467 | |
| 468 | The :class:`Enum` class is callable, providing the following functional API:: |
| 469 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 470 | >>> Animal = Enum('Animal', 'ANT BEE CAT DOG') |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 471 | >>> Animal |
| 472 | <enum 'Animal'> |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 473 | >>> Animal.ANT |
| 474 | <Animal.ANT: 1> |
| 475 | >>> Animal.ANT.value |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 476 | 1 |
| 477 | >>> list(Animal) |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 478 | [<Animal.ANT: 1>, <Animal.BEE: 2>, <Animal.CAT: 3>, <Animal.DOG: 4>] |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 479 | |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 480 | The semantics of this API resemble :class:`~collections.namedtuple`. The first |
| 481 | argument of the call to :class:`Enum` is the name of the enumeration. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 482 | |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 483 | The second argument is the *source* of enumeration member names. It can be a |
| 484 | whitespace-separated string of names, a sequence of names, a sequence of |
| 485 | 2-tuples with key/value pairs, or a mapping (e.g. dictionary) of names to |
| 486 | values. The last two options enable assigning arbitrary values to |
| 487 | enumerations; the others auto-assign increasing integers starting with 1 (use |
| 488 | the ``start`` parameter to specify a different starting value). A |
| 489 | new class derived from :class:`Enum` is returned. In other words, the above |
| 490 | assignment to :class:`Animal` is equivalent to:: |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 491 | |
Ethan Furman | 8a12329 | 2015-01-14 22:31:50 -0800 | [diff] [blame] | 492 | >>> class Animal(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 493 | ... ANT = 1 |
| 494 | ... BEE = 2 |
| 495 | ... CAT = 3 |
| 496 | ... DOG = 4 |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 497 | ... |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 498 | |
Ethan Furman | e256346 | 2013-06-28 19:37:17 -0700 | [diff] [blame] | 499 | The reason for defaulting to ``1`` as the starting number and not ``0`` is |
| 500 | that ``0`` is ``False`` in a boolean sense, but enum members all evaluate |
| 501 | to ``True``. |
| 502 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 503 | Pickling enums created with the functional API can be tricky as frame stack |
| 504 | implementation details are used to try and figure out which module the |
| 505 | enumeration is being created in (e.g. it will fail if you use a utility |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 506 | function in separate module, and also may not work on IronPython or Jython). |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 507 | The solution is to specify the module name explicitly as follows:: |
| 508 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 509 | >>> Animal = Enum('Animal', 'ANT BEE CAT DOG', module=__name__) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 510 | |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 511 | .. warning:: |
| 512 | |
Ethan Furman | 01cc2d5 | 2014-03-03 15:02:04 -0800 | [diff] [blame] | 513 | If ``module`` is not supplied, and Enum cannot determine what it is, |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 514 | the new Enum members will not be unpicklable; to keep errors closer to |
| 515 | the source, pickling will be disabled. |
| 516 | |
Ethan Furman | ca1b794 | 2014-02-08 11:36:27 -0800 | [diff] [blame] | 517 | The new pickle protocol 4 also, in some circumstances, relies on |
Martin Panter | bae5d81 | 2016-06-18 03:57:31 +0000 | [diff] [blame] | 518 | :attr:`~definition.__qualname__` being set to the location where pickle will be able |
Ethan Furman | ca1b794 | 2014-02-08 11:36:27 -0800 | [diff] [blame] | 519 | to find the class. For example, if the class was made available in class |
| 520 | SomeData in the global scope:: |
| 521 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 522 | >>> Animal = Enum('Animal', 'ANT BEE CAT DOG', qualname='SomeData.Animal') |
Ethan Furman | ca1b794 | 2014-02-08 11:36:27 -0800 | [diff] [blame] | 523 | |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 524 | The complete signature is:: |
| 525 | |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 526 | Enum(value='NewEnumName', names=<...>, *, module='...', qualname='...', type=<mixed-in class>, start=1) |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 527 | |
Ethan Furman | 01cc2d5 | 2014-03-03 15:02:04 -0800 | [diff] [blame] | 528 | :value: What the new Enum class will record as its name. |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 529 | |
Zachary Ware | dbd1c43 | 2014-03-20 10:01:48 -0500 | [diff] [blame] | 530 | :names: The Enum members. This can be a whitespace or comma separated string |
Ethan Furman | d9925a1 | 2014-09-16 20:35:55 -0700 | [diff] [blame] | 531 | (values will start at 1 unless otherwise specified):: |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 532 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 533 | 'RED GREEN BLUE' | 'RED,GREEN,BLUE' | 'RED, GREEN, BLUE' |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 534 | |
Ethan Furman | 8a12329 | 2015-01-14 22:31:50 -0800 | [diff] [blame] | 535 | or an iterator of names:: |
| 536 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 537 | ['RED', 'GREEN', 'BLUE'] |
Ethan Furman | 8a12329 | 2015-01-14 22:31:50 -0800 | [diff] [blame] | 538 | |
Ethan Furman | 01cc2d5 | 2014-03-03 15:02:04 -0800 | [diff] [blame] | 539 | or an iterator of (name, value) pairs:: |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 540 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 541 | [('CYAN', 4), ('MAGENTA', 5), ('YELLOW', 6)] |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 542 | |
Ethan Furman | 01cc2d5 | 2014-03-03 15:02:04 -0800 | [diff] [blame] | 543 | or a mapping:: |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 544 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 545 | {'CHARTREUSE': 7, 'SEA_GREEN': 11, 'ROSEMARY': 42} |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 546 | |
Ethan Furman | 01cc2d5 | 2014-03-03 15:02:04 -0800 | [diff] [blame] | 547 | :module: name of module where new Enum class can be found. |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 548 | |
Ethan Furman | 01cc2d5 | 2014-03-03 15:02:04 -0800 | [diff] [blame] | 549 | :qualname: where in module new Enum class can be found. |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 550 | |
Ethan Furman | 01cc2d5 | 2014-03-03 15:02:04 -0800 | [diff] [blame] | 551 | :type: type to mix in to new Enum class. |
Ethan Furman | 2da9504 | 2014-03-03 12:42:52 -0800 | [diff] [blame] | 552 | |
Yury Selivanov | 4dde587 | 2015-09-11 00:48:21 -0400 | [diff] [blame] | 553 | :start: number to start counting at if only names are passed in. |
Ethan Furman | d9925a1 | 2014-09-16 20:35:55 -0700 | [diff] [blame] | 554 | |
Berker Peksag | 60efd79 | 2014-09-18 05:23:14 +0300 | [diff] [blame] | 555 | .. versionchanged:: 3.5 |
| 556 | The *start* parameter was added. |
| 557 | |
Ethan Furman | ca1b794 | 2014-02-08 11:36:27 -0800 | [diff] [blame] | 558 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 559 | Derived Enumerations |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 560 | -------------------- |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 561 | |
| 562 | IntEnum |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 563 | ^^^^^^^ |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 564 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 565 | The first variation of :class:`Enum` that is provided is also a subclass of |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 566 | :class:`int`. Members of an :class:`IntEnum` can be compared to integers; |
| 567 | by extension, integer enumerations of different types can also be compared |
| 568 | to each other:: |
| 569 | |
| 570 | >>> from enum import IntEnum |
| 571 | >>> class Shape(IntEnum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 572 | ... CIRCLE = 1 |
| 573 | ... SQUARE = 2 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 574 | ... |
| 575 | >>> class Request(IntEnum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 576 | ... POST = 1 |
| 577 | ... GET = 2 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 578 | ... |
| 579 | >>> Shape == 1 |
| 580 | False |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 581 | >>> Shape.CIRCLE == 1 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 582 | True |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 583 | >>> Shape.CIRCLE == Request.POST |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 584 | True |
| 585 | |
| 586 | However, they still can't be compared to standard :class:`Enum` enumerations:: |
| 587 | |
| 588 | >>> class Shape(IntEnum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 589 | ... CIRCLE = 1 |
| 590 | ... SQUARE = 2 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 591 | ... |
| 592 | >>> class Color(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 593 | ... RED = 1 |
| 594 | ... GREEN = 2 |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 595 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 596 | >>> Shape.CIRCLE == Color.RED |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 597 | False |
| 598 | |
| 599 | :class:`IntEnum` values behave like integers in other ways you'd expect:: |
| 600 | |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 601 | >>> int(Shape.CIRCLE) |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 602 | 1 |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 603 | >>> ['a', 'b', 'c'][Shape.CIRCLE] |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 604 | 'b' |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 605 | >>> [i for i in range(Shape.SQUARE)] |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 606 | [0, 1] |
| 607 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 608 | |
Ethan Furman | 0063ff4 | 2020-09-21 17:23:13 -0700 | [diff] [blame] | 609 | StrEnum |
| 610 | ^^^^^^^ |
| 611 | |
| 612 | The second variation of :class:`Enum` that is provided is also a subclass of |
| 613 | :class:`str`. Members of a :class:`StrEnum` can be compared to strings; |
| 614 | by extension, string enumerations of different types can also be compared |
| 615 | to each other. :class:`StrEnum` exists to help avoid the problem of getting |
| 616 | an incorrect member:: |
| 617 | |
| 618 | >>> class Directions(StrEnum): |
| 619 | ... NORTH = 'north', # notice the trailing comma |
| 620 | ... SOUTH = 'south' |
| 621 | |
| 622 | Before :class:`StrEnum`, ``Directions.NORTH`` would have been the :class:`tuple` |
| 623 | ``('north',)``. |
| 624 | |
Ethan Furman | d986d16 | 2020-09-22 13:00:07 -0700 | [diff] [blame] | 625 | .. note:: |
| 626 | |
| 627 | Unlike other Enum's, ``str(StrEnum.member)`` will return the value of the |
| 628 | member instead of the usual ``"EnumClass.member"``. |
| 629 | |
Ethan Furman | 0063ff4 | 2020-09-21 17:23:13 -0700 | [diff] [blame] | 630 | .. versionadded:: 3.10 |
| 631 | |
| 632 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 633 | IntFlag |
| 634 | ^^^^^^^ |
| 635 | |
| 636 | The next variation of :class:`Enum` provided, :class:`IntFlag`, is also based |
| 637 | on :class:`int`. The difference being :class:`IntFlag` members can be combined |
| 638 | using the bitwise operators (&, \|, ^, ~) and the result is still an |
| 639 | :class:`IntFlag` member. However, as the name implies, :class:`IntFlag` |
Ethan Furman | 54924df | 2016-09-07 23:40:31 -0700 | [diff] [blame] | 640 | members also subclass :class:`int` and can be used wherever an :class:`int` is |
| 641 | used. Any operation on an :class:`IntFlag` member besides the bit-wise |
| 642 | operations will lose the :class:`IntFlag` membership. |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 643 | |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 644 | .. versionadded:: 3.6 |
| 645 | |
| 646 | Sample :class:`IntFlag` class:: |
| 647 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 648 | >>> from enum import IntFlag |
| 649 | >>> class Perm(IntFlag): |
| 650 | ... R = 4 |
| 651 | ... W = 2 |
| 652 | ... X = 1 |
| 653 | ... |
| 654 | >>> Perm.R | Perm.W |
| 655 | <Perm.R|W: 6> |
| 656 | >>> Perm.R + Perm.W |
| 657 | 6 |
| 658 | >>> RW = Perm.R | Perm.W |
| 659 | >>> Perm.R in RW |
| 660 | True |
| 661 | |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 662 | It is also possible to name the combinations:: |
| 663 | |
| 664 | >>> class Perm(IntFlag): |
| 665 | ... R = 4 |
| 666 | ... W = 2 |
| 667 | ... X = 1 |
| 668 | ... RWX = 7 |
| 669 | >>> Perm.RWX |
| 670 | <Perm.RWX: 7> |
| 671 | >>> ~Perm.RWX |
Ethan Furman | 27682d2 | 2016-09-04 11:39:01 -0700 | [diff] [blame] | 672 | <Perm.-8: -8> |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 673 | |
| 674 | Another important difference between :class:`IntFlag` and :class:`Enum` is that |
| 675 | if no flags are set (the value is 0), its boolean evaluation is :data:`False`:: |
| 676 | |
| 677 | >>> Perm.R & Perm.X |
| 678 | <Perm.0: 0> |
| 679 | >>> bool(Perm.R & Perm.X) |
| 680 | False |
| 681 | |
| 682 | Because :class:`IntFlag` members are also subclasses of :class:`int` they can |
| 683 | be combined with them:: |
| 684 | |
| 685 | >>> Perm.X | 8 |
| 686 | <Perm.8|X: 9> |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 687 | |
Ethan Furman | 7219e27 | 2020-09-16 13:01:00 -0700 | [diff] [blame] | 688 | :class:`IntFlag` members can also be iterated over:: |
| 689 | |
| 690 | >>> list(RW) |
| 691 | [<Perm.R: 4>, <Perm.W: 2>] |
| 692 | |
| 693 | .. versionadded:: 3.10 |
| 694 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 695 | |
| 696 | Flag |
| 697 | ^^^^ |
| 698 | |
| 699 | The last variation is :class:`Flag`. Like :class:`IntFlag`, :class:`Flag` |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 700 | members can be combined using the bitwise operators (&, \|, ^, ~). Unlike |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 701 | :class:`IntFlag`, they cannot be combined with, nor compared against, any |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 702 | other :class:`Flag` enumeration, nor :class:`int`. While it is possible to |
| 703 | specify the values directly it is recommended to use :class:`auto` as the |
| 704 | value and let :class:`Flag` select an appropriate value. |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 705 | |
| 706 | .. versionadded:: 3.6 |
| 707 | |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 708 | Like :class:`IntFlag`, if a combination of :class:`Flag` members results in no |
| 709 | flags being set, the boolean evaluation is :data:`False`:: |
| 710 | |
Julian Kahnert | 0f31c74 | 2018-01-13 04:35:57 +0100 | [diff] [blame] | 711 | >>> from enum import Flag, auto |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 712 | >>> class Color(Flag): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 713 | ... RED = auto() |
| 714 | ... BLUE = auto() |
| 715 | ... GREEN = auto() |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 716 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 717 | >>> Color.RED & Color.GREEN |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 718 | <Color.0: 0> |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 719 | >>> bool(Color.RED & Color.GREEN) |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 720 | False |
| 721 | |
Ethan Furman | 27682d2 | 2016-09-04 11:39:01 -0700 | [diff] [blame] | 722 | Individual flags should have values that are powers of two (1, 2, 4, 8, ...), |
| 723 | while combinations of flags won't:: |
| 724 | |
| 725 | >>> class Color(Flag): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 726 | ... RED = auto() |
| 727 | ... BLUE = auto() |
| 728 | ... GREEN = auto() |
| 729 | ... WHITE = RED | BLUE | GREEN |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 730 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 731 | >>> Color.WHITE |
| 732 | <Color.WHITE: 7> |
Ethan Furman | 27682d2 | 2016-09-04 11:39:01 -0700 | [diff] [blame] | 733 | |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 734 | Giving a name to the "no flags set" condition does not change its boolean |
| 735 | value:: |
| 736 | |
| 737 | >>> class Color(Flag): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 738 | ... BLACK = 0 |
| 739 | ... RED = auto() |
| 740 | ... BLUE = auto() |
| 741 | ... GREEN = auto() |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 742 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 743 | >>> Color.BLACK |
| 744 | <Color.BLACK: 0> |
| 745 | >>> bool(Color.BLACK) |
Ethan Furman | 25d94bb | 2016-09-02 16:32:32 -0700 | [diff] [blame] | 746 | False |
| 747 | |
Ethan Furman | 7219e27 | 2020-09-16 13:01:00 -0700 | [diff] [blame] | 748 | :class:`Flag` members can also be iterated over:: |
| 749 | |
| 750 | >>> purple = Color.RED | Color.BLUE |
| 751 | >>> list(purple) |
| 752 | [<Color.BLUE: 2>, <Color.RED: 1>] |
| 753 | |
| 754 | .. versionadded:: 3.10 |
| 755 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 756 | .. note:: |
| 757 | |
| 758 | For the majority of new code, :class:`Enum` and :class:`Flag` are strongly |
| 759 | recommended, since :class:`IntEnum` and :class:`IntFlag` break some |
| 760 | semantic promises of an enumeration (by being comparable to integers, and |
| 761 | thus by transitivity to other unrelated enumerations). :class:`IntEnum` |
| 762 | and :class:`IntFlag` should be used only in cases where :class:`Enum` and |
| 763 | :class:`Flag` will not do; for example, when integer constants are replaced |
| 764 | with enumerations, or for interoperability with other systems. |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 765 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 766 | |
| 767 | Others |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 768 | ^^^^^^ |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 769 | |
| 770 | While :class:`IntEnum` is part of the :mod:`enum` module, it would be very |
| 771 | simple to implement independently:: |
| 772 | |
| 773 | class IntEnum(int, Enum): |
| 774 | pass |
| 775 | |
| 776 | This demonstrates how similar derived enumerations can be defined; for example |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 777 | a :class:`StrEnum` that mixes in :class:`str` instead of :class:`int`. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 778 | |
| 779 | Some rules: |
| 780 | |
| 781 | 1. When subclassing :class:`Enum`, mix-in types must appear before |
| 782 | :class:`Enum` itself in the sequence of bases, as in the :class:`IntEnum` |
| 783 | example above. |
| 784 | 2. While :class:`Enum` can have members of any type, once you mix in an |
| 785 | additional type, all the members must have values of that type, e.g. |
| 786 | :class:`int` above. This restriction does not apply to mix-ins which only |
Antoine | d3c8d73 | 2019-08-20 03:41:31 +0200 | [diff] [blame] | 787 | add methods and don't specify another type. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 788 | 3. When another data type is mixed in, the :attr:`value` attribute is *not the |
Zachary Ware | dbd1c43 | 2014-03-20 10:01:48 -0500 | [diff] [blame] | 789 | same* as the enum member itself, although it is equivalent and will compare |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 790 | equal. |
Martin Panter | d5db147 | 2016-02-08 01:34:09 +0000 | [diff] [blame] | 791 | 4. %-style formatting: `%s` and `%r` call the :class:`Enum` class's |
| 792 | :meth:`__str__` and :meth:`__repr__` respectively; other codes (such as |
| 793 | `%i` or `%h` for IntEnum) treat the enum member as its mixed-in type. |
Martin Panter | bc1ee46 | 2016-02-13 00:41:37 +0000 | [diff] [blame] | 794 | 5. :ref:`Formatted string literals <f-strings>`, :meth:`str.format`, |
thatneat | 2f19e82 | 2019-07-04 11:28:37 -0700 | [diff] [blame] | 795 | and :func:`format` will use the mixed-in type's :meth:`__format__` |
| 796 | unless :meth:`__str__` or :meth:`__format__` is overridden in the subclass, |
| 797 | in which case the overridden methods or :class:`Enum` methods will be used. |
| 798 | Use the !s and !r format codes to force usage of the :class:`Enum` class's |
| 799 | :meth:`__str__` and :meth:`__repr__` methods. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 800 | |
Ethan Furman | f522374 | 2018-09-12 10:00:30 -0700 | [diff] [blame] | 801 | When to use :meth:`__new__` vs. :meth:`__init__` |
| 802 | ------------------------------------------------ |
| 803 | |
| 804 | :meth:`__new__` must be used whenever you want to customize the actual value of |
| 805 | the :class:`Enum` member. Any other modifications may go in either |
| 806 | :meth:`__new__` or :meth:`__init__`, with :meth:`__init__` being preferred. |
| 807 | |
| 808 | For example, if you want to pass several items to the constructor, but only |
| 809 | want one of them to be the value:: |
| 810 | |
| 811 | >>> class Coordinate(bytes, Enum): |
| 812 | ... """ |
| 813 | ... Coordinate with binary codes that can be indexed by the int code. |
| 814 | ... """ |
| 815 | ... def __new__(cls, value, label, unit): |
| 816 | ... obj = bytes.__new__(cls, [value]) |
| 817 | ... obj._value_ = value |
| 818 | ... obj.label = label |
| 819 | ... obj.unit = unit |
| 820 | ... return obj |
| 821 | ... PX = (0, 'P.X', 'km') |
| 822 | ... PY = (1, 'P.Y', 'km') |
| 823 | ... VX = (2, 'V.X', 'km/s') |
| 824 | ... VY = (3, 'V.Y', 'km/s') |
| 825 | ... |
| 826 | |
| 827 | >>> print(Coordinate['PY']) |
| 828 | Coordinate.PY |
| 829 | |
| 830 | >>> print(Coordinate(3)) |
| 831 | Coordinate.VY |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 832 | |
| 833 | Interesting examples |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 834 | -------------------- |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 835 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 836 | While :class:`Enum`, :class:`IntEnum`, :class:`IntFlag`, and :class:`Flag` are |
| 837 | expected to cover the majority of use-cases, they cannot cover them all. Here |
| 838 | are recipes for some different types of enumerations that can be used directly, |
| 839 | or as examples for creating one's own. |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 840 | |
| 841 | |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 842 | Omitting values |
| 843 | ^^^^^^^^^^^^^^^ |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 844 | |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 845 | In many use-cases one doesn't care what the actual value of an enumeration |
| 846 | is. There are several ways to define this type of simple enumeration: |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 847 | |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 848 | - use instances of :class:`auto` for the value |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 849 | - use instances of :class:`object` as the value |
| 850 | - use a descriptive string as the value |
| 851 | - use a tuple as the value and a custom :meth:`__new__` to replace the |
| 852 | tuple with an :class:`int` value |
| 853 | |
| 854 | Using any of these methods signifies to the user that these values are not |
| 855 | important, and also enables one to add, remove, or reorder members without |
| 856 | having to renumber the remaining members. |
| 857 | |
| 858 | Whichever method you choose, you should provide a :meth:`repr` that also hides |
| 859 | the (unimportant) value:: |
| 860 | |
| 861 | >>> class NoValue(Enum): |
| 862 | ... def __repr__(self): |
| 863 | ... return '<%s.%s>' % (self.__class__.__name__, self.name) |
| 864 | ... |
| 865 | |
| 866 | |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 867 | Using :class:`auto` |
| 868 | """"""""""""""""""" |
| 869 | |
Berker Peksag | 2a267a1 | 2017-01-02 05:51:04 +0300 | [diff] [blame] | 870 | Using :class:`auto` would look like:: |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 871 | |
| 872 | >>> class Color(NoValue): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 873 | ... RED = auto() |
| 874 | ... BLUE = auto() |
| 875 | ... GREEN = auto() |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 876 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 877 | >>> Color.GREEN |
| 878 | <Color.GREEN> |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 879 | |
| 880 | |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 881 | Using :class:`object` |
| 882 | """"""""""""""""""""" |
| 883 | |
| 884 | Using :class:`object` would look like:: |
| 885 | |
| 886 | >>> class Color(NoValue): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 887 | ... RED = object() |
| 888 | ... GREEN = object() |
| 889 | ... BLUE = object() |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 890 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 891 | >>> Color.GREEN |
| 892 | <Color.GREEN> |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 893 | |
| 894 | |
| 895 | Using a descriptive string |
| 896 | """""""""""""""""""""""""" |
| 897 | |
| 898 | Using a string as the value would look like:: |
| 899 | |
| 900 | >>> class Color(NoValue): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 901 | ... RED = 'stop' |
| 902 | ... GREEN = 'go' |
| 903 | ... BLUE = 'too fast!' |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 904 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 905 | >>> Color.GREEN |
| 906 | <Color.GREEN> |
| 907 | >>> Color.GREEN.value |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 908 | 'go' |
| 909 | |
| 910 | |
| 911 | Using a custom :meth:`__new__` |
| 912 | """""""""""""""""""""""""""""" |
| 913 | |
| 914 | Using an auto-numbering :meth:`__new__` would look like:: |
| 915 | |
| 916 | >>> class AutoNumber(NoValue): |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 917 | ... def __new__(cls): |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 918 | ... value = len(cls.__members__) + 1 |
| 919 | ... obj = object.__new__(cls) |
Ethan Furman | 9026262 | 2013-07-30 12:24:25 -0700 | [diff] [blame] | 920 | ... obj._value_ = value |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 921 | ... return obj |
| 922 | ... |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 923 | >>> class Color(AutoNumber): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 924 | ... RED = () |
| 925 | ... GREEN = () |
| 926 | ... BLUE = () |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 927 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 928 | >>> Color.GREEN |
| 929 | <Color.GREEN> |
| 930 | >>> Color.GREEN.value |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 931 | 2 |
| 932 | |
Ethan Furman | 62e40d8 | 2020-09-22 00:05:27 -0700 | [diff] [blame] | 933 | To make a more general purpose ``AutoNumber``, add ``*args`` to the signature:: |
| 934 | |
| 935 | >>> class AutoNumber(NoValue): |
| 936 | ... def __new__(cls, *args): # this is the only change from above |
| 937 | ... value = len(cls.__members__) + 1 |
| 938 | ... obj = object.__new__(cls) |
| 939 | ... obj._value_ = value |
| 940 | ... return obj |
| 941 | ... |
| 942 | |
| 943 | Then when you inherit from ``AutoNumber`` you can write your own ``__init__`` |
| 944 | to handle any extra arguments:: |
| 945 | |
| 946 | >>> class Swatch(AutoNumber): |
| 947 | ... def __init__(self, pantone='unknown'): |
| 948 | ... self.pantone = pantone |
| 949 | ... AUBURN = '3497' |
| 950 | ... SEA_GREEN = '1246' |
| 951 | ... BLEACHED_CORAL = () # New color, no Pantone code yet! |
| 952 | ... |
| 953 | >>> Swatch.SEA_GREEN |
| 954 | <Swatch.SEA_GREEN: 2> |
| 955 | >>> Swatch.SEA_GREEN.pantone |
| 956 | '1246' |
| 957 | >>> Swatch.BLEACHED_CORAL.pantone |
| 958 | 'unknown' |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 959 | |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 960 | .. note:: |
| 961 | |
| 962 | The :meth:`__new__` method, if defined, is used during creation of the Enum |
| 963 | members; it is then replaced by Enum's :meth:`__new__` which is used after |
Ethan Furman | f75805e | 2014-09-16 19:13:31 -0700 | [diff] [blame] | 964 | class creation for lookup of existing members. |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 965 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 966 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 967 | OrderedEnum |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 968 | ^^^^^^^^^^^ |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 969 | |
| 970 | An ordered enumeration that is not based on :class:`IntEnum` and so maintains |
| 971 | the normal :class:`Enum` invariants (such as not being comparable to other |
| 972 | enumerations):: |
| 973 | |
| 974 | >>> class OrderedEnum(Enum): |
| 975 | ... def __ge__(self, other): |
| 976 | ... if self.__class__ is other.__class__: |
Ethan Furman | 9026262 | 2013-07-30 12:24:25 -0700 | [diff] [blame] | 977 | ... return self.value >= other.value |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 978 | ... return NotImplemented |
| 979 | ... def __gt__(self, other): |
| 980 | ... if self.__class__ is other.__class__: |
Ethan Furman | 9026262 | 2013-07-30 12:24:25 -0700 | [diff] [blame] | 981 | ... return self.value > other.value |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 982 | ... return NotImplemented |
| 983 | ... def __le__(self, other): |
| 984 | ... if self.__class__ is other.__class__: |
Ethan Furman | 9026262 | 2013-07-30 12:24:25 -0700 | [diff] [blame] | 985 | ... return self.value <= other.value |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 986 | ... return NotImplemented |
| 987 | ... def __lt__(self, other): |
| 988 | ... if self.__class__ is other.__class__: |
Ethan Furman | 9026262 | 2013-07-30 12:24:25 -0700 | [diff] [blame] | 989 | ... return self.value < other.value |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 990 | ... return NotImplemented |
| 991 | ... |
| 992 | >>> class Grade(OrderedEnum): |
| 993 | ... A = 5 |
| 994 | ... B = 4 |
| 995 | ... C = 3 |
| 996 | ... D = 2 |
| 997 | ... F = 1 |
| 998 | ... |
| 999 | >>> Grade.C < Grade.A |
| 1000 | True |
| 1001 | |
| 1002 | |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 1003 | DuplicateFreeEnum |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 1004 | ^^^^^^^^^^^^^^^^^ |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 1005 | |
| 1006 | Raises an error if a duplicate member name is found instead of creating an |
| 1007 | alias:: |
| 1008 | |
| 1009 | >>> class DuplicateFreeEnum(Enum): |
| 1010 | ... def __init__(self, *args): |
| 1011 | ... cls = self.__class__ |
| 1012 | ... if any(self.value == e.value for e in cls): |
| 1013 | ... a = self.name |
| 1014 | ... e = cls(self.value).name |
| 1015 | ... raise ValueError( |
| 1016 | ... "aliases not allowed in DuplicateFreeEnum: %r --> %r" |
| 1017 | ... % (a, e)) |
| 1018 | ... |
| 1019 | >>> class Color(DuplicateFreeEnum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 1020 | ... RED = 1 |
| 1021 | ... GREEN = 2 |
| 1022 | ... BLUE = 3 |
| 1023 | ... GRENE = 2 |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 1024 | ... |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 1025 | Traceback (most recent call last): |
| 1026 | ... |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 1027 | ValueError: aliases not allowed in DuplicateFreeEnum: 'GRENE' --> 'GREEN' |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 1028 | |
| 1029 | .. note:: |
| 1030 | |
| 1031 | This is a useful example for subclassing Enum to add or change other |
Ezio Melotti | 93d7dda | 2013-10-05 04:13:18 +0300 | [diff] [blame] | 1032 | behaviors as well as disallowing aliases. If the only desired change is |
Ezio Melotti | 17f1edd | 2013-10-05 04:26:06 +0300 | [diff] [blame] | 1033 | disallowing aliases, the :func:`unique` decorator can be used instead. |
Ethan Furman | f24bb35 | 2013-07-18 17:05:39 -0700 | [diff] [blame] | 1034 | |
| 1035 | |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 1036 | Planet |
Ethan Furman | ed0bf8a | 2013-09-06 19:53:30 -0700 | [diff] [blame] | 1037 | ^^^^^^ |
Ethan Furman | 6b3d64a | 2013-06-14 16:55:46 -0700 | [diff] [blame] | 1038 | |
| 1039 | If :meth:`__new__` or :meth:`__init__` is defined the value of the enum member |
| 1040 | will be passed to those methods:: |
| 1041 | |
| 1042 | >>> class Planet(Enum): |
| 1043 | ... MERCURY = (3.303e+23, 2.4397e6) |
| 1044 | ... VENUS = (4.869e+24, 6.0518e6) |
| 1045 | ... EARTH = (5.976e+24, 6.37814e6) |
| 1046 | ... MARS = (6.421e+23, 3.3972e6) |
| 1047 | ... JUPITER = (1.9e+27, 7.1492e7) |
| 1048 | ... SATURN = (5.688e+26, 6.0268e7) |
| 1049 | ... URANUS = (8.686e+25, 2.5559e7) |
| 1050 | ... NEPTUNE = (1.024e+26, 2.4746e7) |
| 1051 | ... def __init__(self, mass, radius): |
| 1052 | ... self.mass = mass # in kilograms |
| 1053 | ... self.radius = radius # in meters |
| 1054 | ... @property |
| 1055 | ... def surface_gravity(self): |
| 1056 | ... # universal gravitational constant (m3 kg-1 s-2) |
| 1057 | ... G = 6.67300E-11 |
| 1058 | ... return G * self.mass / (self.radius * self.radius) |
| 1059 | ... |
| 1060 | >>> Planet.EARTH.value |
| 1061 | (5.976e+24, 6378140.0) |
| 1062 | >>> Planet.EARTH.surface_gravity |
| 1063 | 9.802652743337129 |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1064 | |
| 1065 | |
Ethan Furman | a4b1bb4 | 2018-01-22 07:56:37 -0800 | [diff] [blame] | 1066 | TimePeriod |
| 1067 | ^^^^^^^^^^ |
| 1068 | |
| 1069 | An example to show the :attr:`_ignore_` attribute in use:: |
| 1070 | |
| 1071 | >>> from datetime import timedelta |
| 1072 | >>> class Period(timedelta, Enum): |
| 1073 | ... "different lengths of time" |
| 1074 | ... _ignore_ = 'Period i' |
| 1075 | ... Period = vars() |
| 1076 | ... for i in range(367): |
| 1077 | ... Period['day_%d' % i] = i |
| 1078 | ... |
| 1079 | >>> list(Period)[:2] |
| 1080 | [<Period.day_0: datetime.timedelta(0)>, <Period.day_1: datetime.timedelta(days=1)>] |
| 1081 | >>> list(Period)[-2:] |
| 1082 | [<Period.day_365: datetime.timedelta(days=365)>, <Period.day_366: datetime.timedelta(days=366)>] |
| 1083 | |
| 1084 | |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1085 | How are Enums different? |
| 1086 | ------------------------ |
| 1087 | |
| 1088 | Enums have a custom metaclass that affects many aspects of both derived Enum |
| 1089 | classes and their instances (members). |
| 1090 | |
| 1091 | |
| 1092 | Enum Classes |
| 1093 | ^^^^^^^^^^^^ |
| 1094 | |
| 1095 | The :class:`EnumMeta` metaclass is responsible for providing the |
| 1096 | :meth:`__contains__`, :meth:`__dir__`, :meth:`__iter__` and other methods that |
| 1097 | allow one to do things with an :class:`Enum` class that fail on a typical |
Rahul Jha | 9430652 | 2018-09-10 23:51:04 +0530 | [diff] [blame] | 1098 | class, such as `list(Color)` or `some_enum_var in Color`. :class:`EnumMeta` is |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1099 | responsible for ensuring that various other methods on the final :class:`Enum` |
| 1100 | class are correct (such as :meth:`__new__`, :meth:`__getnewargs__`, |
Martin Panter | d21e0b5 | 2015-10-10 10:36:22 +0000 | [diff] [blame] | 1101 | :meth:`__str__` and :meth:`__repr__`). |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1102 | |
| 1103 | |
| 1104 | Enum Members (aka instances) |
| 1105 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 1106 | |
| 1107 | The most interesting thing about Enum members is that they are singletons. |
| 1108 | :class:`EnumMeta` creates them all while it is creating the :class:`Enum` |
| 1109 | class itself, and then puts a custom :meth:`__new__` in place to ensure |
| 1110 | that no new ones are ever instantiated by returning only the existing |
| 1111 | member instances. |
| 1112 | |
| 1113 | |
| 1114 | Finer Points |
| 1115 | ^^^^^^^^^^^^ |
| 1116 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1117 | Supported ``__dunder__`` names |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 1118 | """""""""""""""""""""""""""""" |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1119 | |
INADA Naoki | e57f91a | 2018-06-19 01:14:26 +0900 | [diff] [blame] | 1120 | :attr:`__members__` is a read-only ordered mapping of ``member_name``:``member`` |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1121 | items. It is only available on the class. |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1122 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1123 | :meth:`__new__`, if specified, must create and return the enum members; it is |
| 1124 | also a very good idea to set the member's :attr:`_value_` appropriately. Once |
| 1125 | all the members are created it is no longer used. |
Ethan Furman | 748dad5 | 2015-11-20 13:12:26 -0800 | [diff] [blame] | 1126 | |
Ethan Furman | 60255b6 | 2016-01-15 15:01:33 -0800 | [diff] [blame] | 1127 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1128 | Supported ``_sunder_`` names |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 1129 | """""""""""""""""""""""""""" |
Ethan Furman | 60255b6 | 2016-01-15 15:01:33 -0800 | [diff] [blame] | 1130 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1131 | - ``_name_`` -- name of the member |
| 1132 | - ``_value_`` -- value of the member; can be set / modified in ``__new__`` |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1133 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1134 | - ``_missing_`` -- a lookup function used when a value is not found; may be |
| 1135 | overridden |
Antoine | d3c8d73 | 2019-08-20 03:41:31 +0200 | [diff] [blame] | 1136 | - ``_ignore_`` -- a list of names, either as a :class:`list` or a :class:`str`, |
Ethan Furman | a4b1bb4 | 2018-01-22 07:56:37 -0800 | [diff] [blame] | 1137 | that will not be transformed into members, and will be removed from the final |
| 1138 | class |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1139 | - ``_order_`` -- used in Python 2/3 code to ensure member order is consistent |
| 1140 | (class attribute, removed during class creation) |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 1141 | - ``_generate_next_value_`` -- used by the `Functional API`_ and by |
| 1142 | :class:`auto` to get an appropriate value for an enum member; may be |
| 1143 | overridden |
Ethan Furman | 9a1daf5 | 2013-09-27 22:58:06 -0700 | [diff] [blame] | 1144 | |
Ethan Furman | c16595e | 2016-09-10 23:36:59 -0700 | [diff] [blame] | 1145 | .. versionadded:: 3.6 ``_missing_``, ``_order_``, ``_generate_next_value_`` |
Ethan Furman | a4b1bb4 | 2018-01-22 07:56:37 -0800 | [diff] [blame] | 1146 | .. versionadded:: 3.7 ``_ignore_`` |
Ethan Furman | 332dbc7 | 2016-08-20 00:00:52 -0700 | [diff] [blame] | 1147 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1148 | To help keep Python 2 / Python 3 code in sync an :attr:`_order_` attribute can |
| 1149 | be provided. It will be checked against the actual order of the enumeration |
| 1150 | and raise an error if the two do not match:: |
Ethan Furman | e8e6127 | 2016-08-20 07:19:31 -0700 | [diff] [blame] | 1151 | |
| 1152 | >>> class Color(Enum): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 1153 | ... _order_ = 'RED GREEN BLUE' |
| 1154 | ... RED = 1 |
| 1155 | ... BLUE = 3 |
| 1156 | ... GREEN = 2 |
Ethan Furman | e8e6127 | 2016-08-20 07:19:31 -0700 | [diff] [blame] | 1157 | ... |
| 1158 | Traceback (most recent call last): |
| 1159 | ... |
| 1160 | TypeError: member order does not match _order_ |
| 1161 | |
| 1162 | .. note:: |
| 1163 | |
| 1164 | In Python 2 code the :attr:`_order_` attribute is necessary as definition |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1165 | order is lost before it can be recorded. |
| 1166 | |
Ethan Furman | 7cf0aad | 2020-12-09 17:12:11 -0800 | [diff] [blame^] | 1167 | |
| 1168 | _Private__names |
| 1169 | """"""""""""""" |
| 1170 | |
| 1171 | Private names are not converted to Enum members, but remain normal attributes. |
| 1172 | |
| 1173 | .. versionchanged:: 3.10 |
| 1174 | |
| 1175 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1176 | ``Enum`` member type |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 1177 | """""""""""""""""""" |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1178 | |
Ethan Furman | 54924df | 2016-09-07 23:40:31 -0700 | [diff] [blame] | 1179 | :class:`Enum` members are instances of their :class:`Enum` class, and are |
| 1180 | normally accessed as ``EnumClass.member``. Under certain circumstances they |
| 1181 | can also be accessed as ``EnumClass.member.member``, but you should never do |
| 1182 | this as that lookup may fail or, worse, return something besides the |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 1183 | :class:`Enum` member you are looking for (this is another good reason to use |
| 1184 | all-uppercase names for members):: |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1185 | |
| 1186 | >>> class FieldTypes(Enum): |
| 1187 | ... name = 0 |
| 1188 | ... value = 1 |
| 1189 | ... size = 2 |
| 1190 | ... |
| 1191 | >>> FieldTypes.value.size |
| 1192 | <FieldTypes.size: 2> |
| 1193 | >>> FieldTypes.size.value |
| 1194 | 2 |
| 1195 | |
| 1196 | .. versionchanged:: 3.5 |
| 1197 | |
| 1198 | |
Ethan Furman | 0063ff4 | 2020-09-21 17:23:13 -0700 | [diff] [blame] | 1199 | Creating members that are mixed with other data types |
| 1200 | """"""""""""""""""""""""""""""""""""""""""""""""""""" |
| 1201 | |
| 1202 | When subclassing other data types, such as :class:`int` or :class:`str`, with |
| 1203 | an :class:`Enum`, all values after the `=` are passed to that data type's |
| 1204 | constructor. For example:: |
| 1205 | |
| 1206 | >>> class MyEnum(IntEnum): |
| 1207 | ... example = '11', 16 # '11' will be interpreted as a hexadecimal |
| 1208 | ... # number |
| 1209 | >>> MyEnum.example |
| 1210 | <MyEnum.example: 17> |
| 1211 | |
| 1212 | |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1213 | Boolean value of ``Enum`` classes and members |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 1214 | """"""""""""""""""""""""""""""""""""""""""""" |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1215 | |
Ethan Furman | 54924df | 2016-09-07 23:40:31 -0700 | [diff] [blame] | 1216 | :class:`Enum` members that are mixed with non-:class:`Enum` types (such as |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1217 | :class:`int`, :class:`str`, etc.) are evaluated according to the mixed-in |
Ethan Furman | 54924df | 2016-09-07 23:40:31 -0700 | [diff] [blame] | 1218 | type's rules; otherwise, all members evaluate as :data:`True`. To make your |
| 1219 | own Enum's boolean evaluation depend on the member's value add the following to |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1220 | your class:: |
| 1221 | |
| 1222 | def __bool__(self): |
| 1223 | return bool(self.value) |
| 1224 | |
Ethan Furman | 54924df | 2016-09-07 23:40:31 -0700 | [diff] [blame] | 1225 | :class:`Enum` classes always evaluate as :data:`True`. |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1226 | |
| 1227 | |
| 1228 | ``Enum`` classes with methods |
Ethan Furman | 6a137e8 | 2016-09-07 08:17:15 -0700 | [diff] [blame] | 1229 | """"""""""""""""""""""""""""" |
Ethan Furman | 65a5a47 | 2016-09-01 23:55:19 -0700 | [diff] [blame] | 1230 | |
| 1231 | If you give your :class:`Enum` subclass extra methods, like the `Planet`_ |
| 1232 | class above, those methods will show up in a :func:`dir` of the member, |
| 1233 | but not of the class:: |
| 1234 | |
| 1235 | >>> dir(Planet) |
| 1236 | ['EARTH', 'JUPITER', 'MARS', 'MERCURY', 'NEPTUNE', 'SATURN', 'URANUS', 'VENUS', '__class__', '__doc__', '__members__', '__module__'] |
| 1237 | >>> dir(Planet.EARTH) |
| 1238 | ['__class__', '__doc__', '__module__', 'name', 'surface_gravity', 'value'] |
| 1239 | |
Ethan Furman | 3515dcc | 2016-09-18 13:15:41 -0700 | [diff] [blame] | 1240 | |
| 1241 | Combining members of ``Flag`` |
| 1242 | """"""""""""""""""""""""""""" |
| 1243 | |
| 1244 | If a combination of Flag members is not named, the :func:`repr` will include |
| 1245 | all named flags and all named combinations of flags that are in the value:: |
| 1246 | |
| 1247 | >>> class Color(Flag): |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 1248 | ... RED = auto() |
| 1249 | ... GREEN = auto() |
| 1250 | ... BLUE = auto() |
| 1251 | ... MAGENTA = RED | BLUE |
| 1252 | ... YELLOW = RED | GREEN |
| 1253 | ... CYAN = GREEN | BLUE |
Ethan Furman | 3515dcc | 2016-09-18 13:15:41 -0700 | [diff] [blame] | 1254 | ... |
| 1255 | >>> Color(3) # named combination |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 1256 | <Color.YELLOW: 3> |
Ethan Furman | 3515dcc | 2016-09-18 13:15:41 -0700 | [diff] [blame] | 1257 | >>> Color(7) # not named combination |
Ethan Furman | 23bb6f4 | 2016-11-21 09:22:05 -0800 | [diff] [blame] | 1258 | <Color.CYAN|MAGENTA|BLUE|YELLOW|GREEN|RED: 7> |
Ethan Furman | 3515dcc | 2016-09-18 13:15:41 -0700 | [diff] [blame] | 1259 | |
Ethan Furman | d986d16 | 2020-09-22 13:00:07 -0700 | [diff] [blame] | 1260 | ``StrEnum`` and :meth:`str.__str__` |
| 1261 | """"""""""""""""""""""""""""""""""" |
| 1262 | |
| 1263 | An important difference between :class:`StrEnum` and other Enums is the |
| 1264 | :meth:`__str__` method; because :class:`StrEnum` members are strings, some |
| 1265 | parts of Python will read the string data directly, while others will call |
| 1266 | :meth:`str()`. To make those two operations have the same result, |
| 1267 | :meth:`StrEnum.__str__` will be the same as :meth:`str.__str__` so that |
| 1268 | ``str(StrEnum.member) == StrEnum.member`` is true. |
| 1269 | |