mirror of https://github.com/python/cpython
635 lines
18 KiB
ReStructuredText
635 lines
18 KiB
ReStructuredText
: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 members in definition order
|
|
* uses :meth:`call` syntax to return members by value
|
|
* uses :meth:`index` syntax to return members by name
|
|
|
|
Enumerations are created either by using the :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 the :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 *enum 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`.
|
|
|
|
:class:`StrEnum`
|
|
|
|
Base class for creating enumerated constants that are also
|
|
subclasses of :class:`str`.
|
|
|
|
: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`.
|
|
|
|
: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:`global_enum`
|
|
|
|
:class:`Enum` class decorator to apply the appropriate global `__repr__`,
|
|
and export its members into the global name space.
|
|
|
|
:func:`.property`
|
|
|
|
Allows :class:`Enum` members to have attributes without conflicting with
|
|
other members' names.
|
|
|
|
:func:`unique`
|
|
|
|
Enum class decorator that ensures only one name is bound to any one value.
|
|
|
|
|
|
.. versionadded:: 3.6 ``Flag``, ``IntFlag``, ``auto``
|
|
.. versionadded:: 3.10 ``StrEnum``
|
|
|
|
|
|
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.
|
|
|
|
.. 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__', '__doc__', '__members__', '__module__']
|
|
|
|
.. method:: EnumType.__getattr__(cls, name)
|
|
|
|
Returns the Enum member in *cls* matching *name*, or raises an :exc:`AttributeError`::
|
|
|
|
>>> Color.GREEN
|
|
Color.GREEN
|
|
|
|
.. method:: EnumType.__getitem__(cls, name)
|
|
|
|
Returns the Enum member in *cls* matching *name*, or raises an :exc:`KeyError`::
|
|
|
|
>>> Color['BLUE']
|
|
Color.BLUE
|
|
|
|
.. method:: EnumType.__iter__(cls)
|
|
|
|
Returns each member in *cls* in definition order::
|
|
|
|
>>> list(Color)
|
|
[Color.RED, Color.GREEN, Color.BLUE]
|
|
|
|
.. 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, Color.GREEN, Color.RED]
|
|
|
|
|
|
.. 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. Care must be taken if you mix
|
|
:class:`auto` with other values.
|
|
|
|
.. attribute:: Enum._ignore_
|
|
|
|
``_ignore_`` is only used during creation and is removed from the
|
|
enumeration once that 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.__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:
|
|
|
|
: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:: 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).naem)
|
|
>>> dir(Weekday.SATURDAY)
|
|
['__class__', '__doc__', '__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 (count + 1) * 3
|
|
... FIRST = auto()
|
|
... SECOND = auto()
|
|
>>> PowersOfThree.SECOND.value
|
|
6
|
|
|
|
.. 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
|
|
|
|
.. method:: Enum.__repr__(self)
|
|
|
|
Returns the string used for *repr()* calls. By default, returns the
|
|
*Enum* name and the member name, but can be overridden::
|
|
|
|
>>> class OldStyle(Enum):
|
|
... RETRO = auto()
|
|
... OLD_SCHOOl = auto()
|
|
... YESTERYEAR = auto()
|
|
... def __repr__(self):
|
|
... cls_name = self.__class__.__name__
|
|
... return f'<{cls_name}.{self.name}: {self.value}>'
|
|
>>> OldStyle.RETRO
|
|
<OldStyle.RETRO: 1>
|
|
|
|
.. method:: Enum.__str__(self)
|
|
|
|
Returns the string used for *str()* calls. By default, returns the
|
|
member name, but can be overridden::
|
|
|
|
>>> class OldStyle(Enum):
|
|
... RETRO = auto()
|
|
... OLD_SCHOOl = auto()
|
|
... YESTERYEAR = auto()
|
|
... def __str__(self):
|
|
... cls_name = self.__class__.__name__
|
|
... return f'{cls_name}.{self.name}'
|
|
>>> OldStyle.RETRO
|
|
OldStyle.RETRO
|
|
|
|
.. note::
|
|
|
|
Using :class:`auto` with :class:`Enum` results in integers of increasing value,
|
|
starting with ``1``.
|
|
|
|
|
|
.. 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 Numbers(IntEnum):
|
|
... ONE = 1
|
|
... TWO = 2
|
|
... THREE = 3
|
|
>>> Numbers.THREE
|
|
Numbers.THREE
|
|
>>> Numbers.ONE + Numbers.TWO
|
|
3
|
|
>>> Numbers.THREE + 5
|
|
8
|
|
>>> Numbers.THREE == 3
|
|
True
|
|
|
|
.. note::
|
|
|
|
Using :class:`auto` with :class:`IntEnum` results in integers of increasing value,
|
|
starting with ``1``.
|
|
|
|
|
|
.. 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(str, unknown)``), and in those locations you
|
|
will need to use ``str(StrEnum.member)``.
|
|
|
|
|
|
.. note::
|
|
|
|
Using :class:`auto` with :class:`StrEnum` results in values of the member name,
|
|
lower-cased.
|
|
|
|
|
|
.. 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 members::
|
|
|
|
>>> list(Color.RED)
|
|
[Color.RED]
|
|
>>> list(purple)
|
|
[Color.RED, Color.BLUE]
|
|
|
|
.. 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|Color.GREEN
|
|
|
|
.. method:: __and__(self, other)
|
|
|
|
Returns current flag binary and'ed with other::
|
|
|
|
>>> purple & white
|
|
Color.RED|Color.BLUE
|
|
>>> purple & Color.GREEN
|
|
0x0
|
|
|
|
.. method:: __xor__(self, other)
|
|
|
|
Returns current flag binary xor'ed with other::
|
|
|
|
>>> purple ^ white
|
|
Color.GREEN
|
|
>>> purple ^ Color.GREEN
|
|
Color.RED|Color.GREEN|Color.BLUE
|
|
|
|
.. method:: __invert__(self):
|
|
|
|
Returns all the flags in *type(self)* that are not in self::
|
|
|
|
>>> ~white
|
|
0x0
|
|
>>> ~purple
|
|
Color.GREEN
|
|
>>> ~Color.RED
|
|
Color.GREEN|Color.BLUE
|
|
|
|
.. note::
|
|
|
|
Using :class:`auto` with :class:`Flag` results in integers that are powers
|
|
of two, starting with ``1``.
|
|
|
|
|
|
.. 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
|
|
0x0
|
|
>>> Color.RED | 2
|
|
Color.RED|Color.GREEN
|
|
|
|
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
|
|
|
|
.. note::
|
|
|
|
Using :class:`auto` with :class:`IntFlag` results in integers that are powers
|
|
of two, starting with ``1``.
|
|
|
|
.. 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
|
|
>>> class StrictFlag(Flag, boundary=STRICT):
|
|
... RED = auto()
|
|
... GREEN = auto()
|
|
... BLUE = auto()
|
|
>>> StrictFlag(2**2 + 2**4)
|
|
Traceback (most recent call last):
|
|
...
|
|
ValueError: 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
|
|
>>> class ConformFlag(Flag, boundary=CONFORM):
|
|
... RED = auto()
|
|
... GREEN = auto()
|
|
... BLUE = auto()
|
|
>>> ConformFlag(2**2 + 2**4)
|
|
ConformFlag.BLUE
|
|
|
|
.. attribute:: EJECT
|
|
|
|
Out-of-range values lose their *Flag* membership and revert to :class:`int`.
|
|
This is the default for :class:`IntFlag`::
|
|
|
|
>>> from enum import Flag, EJECT
|
|
>>> 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
|
|
used for some stdlib flags:
|
|
|
|
>>> from enum import Flag, KEEP
|
|
>>> class KeepFlag(Flag, boundary=KEEP):
|
|
... RED = auto()
|
|
... GREEN = auto()
|
|
... BLUE = auto()
|
|
>>> KeepFlag(2**2 + 2**4)
|
|
KeepFlag.BLUE|0x10
|
|
|
|
.. versionadded:: 3.10 ``FlagBoundary``
|
|
|
|
|
|
Utilites and Decorators
|
|
-----------------------
|
|
|
|
.. class:: auto
|
|
|
|
*auto* can be used in place of a value. If used, the *Enum* machinery will
|
|
call an *Enum*'s :meth:`_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 last value; for *StrEnum* it will be the lower-cased version of the
|
|
member's name.
|
|
|
|
``_generate_next_value_`` can be overridden to customize the values used by
|
|
*auto*.
|
|
|
|
.. decorator:: global_enum
|
|
|
|
A :keyword:`class` decorator specifically for enumerations. It replaces the
|
|
:meth:`__repr__` method with one that shows *module_name*.*member_name*. It
|
|
also injects the members, and their aliases, into the global namespace they
|
|
were defined in.
|
|
|
|
.. versionadded:: 3.10
|
|
|
|
.. 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:: 3.10
|
|
|
|
.. decorator:: unique
|
|
|
|
A :keyword:`class` decorator specifically for enumerations. It searches an
|
|
enumeration's :attr:`__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
|