enum — 支持枚举 ¶

3.4 版新增。

源代码： Lib/enum.py

---

枚举：

• is a set of symbolic names (members) bound to unique values

• can be iterated over to return its members in definition order

• 使用 call syntax to return members by value

• 使用 index 句法以按名称返回成员

Enumerations are created either by using 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 class 句法能创建 Enum, 但 Enum 不是正常 Python 类。见 枚举有什么不同？ 了解更多细节。

注意

Nomenclature

• 类 Color 是 enumeration (或 enum )

• 属性 Color.RED , Color.GREEN ，等，是 enumeration 成员 (或 members ) 且功能上均是常量。

• 枚举成员拥有 名称 and 值 (名称对于 Color.RED is RED ，值对于 Color.BLUE is 3 ，等)

---

模块内容 ¶

EnumType

type 对于 Enum 及其子类。

Enum

Base class for creating enumerated constants.

IntEnum

Base class for creating enumerated constants that are also subclasses of int . ( 注意事项 )

StrEnum

Base class for creating enumerated constants that are also subclasses of str . ( 注意事项 )

Flag

Base class for creating enumerated constants that can be combined using the bitwise operations without losing their Flag 成员资格。

IntFlag

Base class for creating enumerated constants that can be combined using the bitwise operators without losing their IntFlag 成员资格。 IntFlag 成员也是子类的 int . ( 注意事项 )

EnumCheck

An enumeration with the values CONTINUOUS , NAMED_FLAGS ，和 UNIQUE , for use with verify() to ensure various constraints are met by a given enumeration.

FlagBoundary

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

auto

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

property()

Allows Enum members to have attributes without conflicting with member names.

unique()

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

verify()

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

member()

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

nonmember()

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

3.6 版新增： Flag , IntFlag , auto

3.11 版新增： StrEnum , EnumCheck , FlagBoundary , property , member , nonmember

---

数据类型 ¶

class enum. EnumType ¶

EnumType 是 metaclass for enum 枚举。它是可能的子类 EnumType – 见 Subclassing EnumType 了解细节。

EnumType is responsible for setting the correct __repr__() , __str__() , __format__() ，和 __reduce__() methods on the final enum , as well as creating the enum members, properly handling duplicates, providing iteration over the enum class, etc.

__contains__ ( cls , member ) ¶

返回 True if member belongs to the cls :

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

注意

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.

__dir__ ( cls ) ¶

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

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

__getattr__ ( cls , name ) ¶

Returns the Enum member in cls matching name ，或引发 AttributeError :

>>> Color.GREEN
<Color.GREEN: 2>
						

__getitem__ ( cls , name ) ¶

Returns the Enum member in cls matching name ，或引发 KeyError :

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

__iter__ ( cls ) ¶

Returns each member in cls in definition order:

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

__len__ ( cls ) ¶

Returns the number of member in cls :

>>> len(Color)
3
						

__reversed__ ( cls ) ¶

Returns each member in cls in reverse definition order:

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

class enum. Enum ¶

Enum is the base class for all enum enumerations.

name ¶

The name used to define the Enum 成员：

>>> Color.BLUE.name
'BLUE'
						

value ¶

The value given to the Enum 成员：

>>> Color.RED.value
1
						

注意

枚举成员值

成员值可以是任何值： int , str , etc.. If the exact value is unimportant you may use auto instances and an appropriate value will be chosen for you. Care must be taken if you mix auto with other values.

_ignore_ ¶

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

_ignore_ is a list of names that will not become members, and whose names will also be removed from the completed enumeration. See TimePeriod 范例。

__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.

  值

  The value to lookup.

• 要使用 cls enum to create a new enum:

cls

The enum class being called.

值

The name of the new Enum to create.

名称

The names/values of the members for the new Enum.

模块

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 auto )

boundary

How to handle out-of-range values from bit operations ( Flag only)

__dir__ ( self ) ¶

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

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

_generate_next_value_ ( name , start , count , last_values ) ¶

名称

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 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
					

__init_subclass__ ( cls , \**kwds ) ¶

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

_missing_ ( cls , value ) ¶

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

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

__repr__ ( self ) ¶

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

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

__str__ ( self ) ¶

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

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

__format__ ( self ) ¶

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

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

注意

使用 auto with Enum results in integers of increasing value, starting with 1 .

class enum. IntEnum ¶

IntEnum 如同 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: 3>
>>> Numbers.ONE + Numbers.TWO
3
>>> Numbers.THREE + 5
8
>>> Numbers.THREE == 3
True
			

注意

使用 auto with IntEnum results in integers of increasing value, starting with 1 .

3.11 版改变： __str__() 现为 int.__str__() to better support the replacement of existing constants use-case. __format__() was already int.__format__() for that same reason.

class enum. StrEnum ¶

StrEnum 如同 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.

注意

There are places in the stdlib that check for an exact str 而不是 str subclass (i.e. type(unknown) == str 而不是 isinstance(str, unknown) ), and in those locations you will need to use str(StrEnum.member) .

注意

使用 auto with StrEnum results in the lower-cased member name as the value.

注意

__str__() is str.__str__() to better support the replacement of existing constants use-case. __format__() is likewise str.__format__() for that same reason.

3.11 版新增。

class enum. 标志 ¶

标志 members support the bitwise operators & ( AND ), | ( OR ), ^ ( XOR )，和 ~ ( INVERT ); the results of those operators are members of the enumeration.

__contains__ ( self , value ) ¶

返回 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
			

__iter__(self):

Returns all contained members:

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

__len__(self):

Returns number of members in flag:

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

__bool__(self):

返回 True if any members in flag, False 否则：

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

__or__ ( self , other ) ¶

Returns current flag binary or’ed with other:

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

__and__ ( self , other ) ¶

Returns current flag binary and’ed with other:

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

__xor__ ( self , other ) ¶

Returns current flag binary xor’ed with other:

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

__invert__(self):

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

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

_numeric_repr_ ( ) ¶

Function used to format any remaining unnamed numeric values. Default is the value’s repr; common choices are hex() and oct() .

注意

使用 auto with Flag results in integers that are powers of two, starting with 1 .

3.11 版改变： repr() of zero-valued flags has changed. It is now::

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

class enum. IntFlag ¶

IntFlag 如同 标志 , but its members are also integers and can be used anywhere that an integer can be used.

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

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

>>> Color.RED + 2
3
										

若 标志 operation is performed with an IntFlag member and:

• the result is a valid IntFlag ： IntFlag is returned

• the result is not a valid IntFlag : the result depends on the FlagBoundary 设置

repr() of unnamed zero-valued flags has changed. It is now:

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

注意

使用 auto with IntFlag results in integers that are powers of two, starting with 1 .

3.11 版改变： __str__() 现为 int.__str__() to better support the replacement of existing constants use-case. __format__() was already int.__format__() for that same reason.

class enum. EnumCheck ¶

EnumCheck contains the options used by the verify() decorator to ensure various constraints; failed constraints result in a ValueError .

UNIQUE ¶

Ensure that each value has only one name:

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

CONTINUOUS ¶

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

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

NAMED_FLAGS ¶

Ensure that any flag groups/masks contain only named flags – useful when values are specified instead of being generated by auto()

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

注意

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

3.11 版新增。

class enum. FlagBoundary ¶

FlagBoundary controls how out-of-range values are handled in 标志 and its subclasses.

STRICT ¶

Out-of-range values cause a ValueError to be raised. This is the default for 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: <flag 'StrictFlag'> invalid value 20
    given 0b0 10100
  allowed 0b0 00111
												

CONFORM ¶

Out-of-range values have invalid values removed, leaving a valid 标志 值：

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

EJECT ¶

Out-of-range values lose their 标志 membership and revert to int . This is the default for IntFlag :

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

KEEP ¶

Out-of-range values are kept, and the 标志 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|16: 20>
															

3.11 版新增。

---

支持 __dunder__ 名称 ¶

__members__ 是只读有序映射的 member_name : member 项。只可用于 class。

__new__() , if specified, must create and return the enum members; it is also a very good idea to set the member’s _value_ appropriately. Once all the members are created it is no longer used.

支持 _sunder_ 名称 ¶

• _name_ – 成员名称

• _value_ – 成员的值；设置/修改可以在 __new__

• _missing_ – a lookup function used when a value is not found; may be overridden

• _ignore_ – a list of names, either as a list 或 str , that will not be transformed into members, and will be removed from the final class

• _order_ – used in Python 2/3 code to ensure member order is consistent (class attribute, removed during class creation)

• _generate_next_value_ – used to get an appropriate value for an enum member; may be overridden

  注意

  For standard Enum classes the next value chosen is the last value seen incremented by one.

  For Flag classes the next value chosen will be the next highest power-of-two, regardless of the last value seen.

3.6 版新增： _missing_ , _order_ , _generate_next_value_

3.7 版新增： _ignore_

---

实用工具和装饰器 ¶

class enum. auto ¶

auto can be used in place of a value. If used, the Enum machinery will call an Enum ’s _generate_next_value_() to get an appropriate value. For Enum and IntEnum that appropriate value will be the last value plus one; for 标志 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 .

注意

in 3.13 the default "generate_next_value_ will always return the highest member value incremented by 1, and will fail if any member is an incompatible type.

@ enum. 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.

注意

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 .

3.11 版新增。

@ enum. unique ¶

A class decorator specifically for enumerations. It searches an enumeration’s __members__ , gathering any aliases it finds; if any are found 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
																

@ enum. verify ¶

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

3.11 版新增。

@ enum. member ¶

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

3.11 版新增。

@ enum. nonmember ¶

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

3.11 版新增。

---

注意事项 ¶

IntEnum , StrEnum ，和 IntFlag

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

• __str__ uses the value and not the name of the enum member

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

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

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

or you can reassign the appropriate str() , etc., in your enum:

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

内容表

• enum — 支持枚举
  • 模块内容
  • 数据类型
    • 支持 __dunder__ 名称
    • 支持 _sunder_ 名称
  • 实用工具和装饰器
  • 注意事项

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