New in version 3.4.
Source code:
———
An enumeration:
is a set of symbolic names (members) bound to unique values
can be iterated over to return its canonical (i.e. non-alias) members in definition order
uses call syntax to return members by value
uses index syntax to return members by name
Enumerations are created either by using
syntax, or by using function-call syntax:
>>> fromenumimportEnum>>> # class syntax>>> classColor(Enum):... RED=1... GREEN=2... BLUE=3>>> # functional syntax>>> Color=Enum('Color',['RED','GREEN','BLUE'])Even though we can use
syntax to create Enums, Enums are not normal Python classes. See
for more details.
Note
Nomenclature
The class Color is an enumeration (or enum)
The attributes Color.RED, Color.GREEN, etc., are enumeration members (or members) and are functionally constants.
The enum members have names and values (the name of Color.RED is RED, the value of Color.BLUE is 3, etc.)
———
Module Contents
The type for Enum and its subclasses.
Base class for creating enumerated constants.
Base class for creating enumerated constants that are also subclasses of
. (
)
Base class for creating enumerated constants that are also subclasses of
. (
)
Base class for creating enumerated constants that can be combined using the bitwise operations without losing their
membership.
Base class for creating enumerated constants that can be combined using the bitwise operators without losing their
membership.
members are also subclasses of
. (
)
Used by
,
, and
to keep the
of the mixed-in type.
An enumeration with the values CONTINUOUS, NAMED_FLAGS, and UNIQUE, for use with
to ensure various constraints are met by a given enumeration.
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.
Instances are replaced with an appropriate value for Enum members.
defaults to the lower-cased version of the member name, while other Enums default to 1 and increase from there.
Allows
members to have attributes without conflicting with member names.
Enum class decorator that ensures only one name is bound to any one value.
Enum class decorator that checks user-selectable constraints on an enumeration.
Make obj a member. Can be used as a decorator.
Do not make obj a member. Can be used as a decorator.
Modify the
and
of an enum to show its members as belonging to the module instead of its class, and export the enum members to the global namespace.
Return a list of all power-of-two integers contained in a flag.
New in version 3.6: Flag, IntFlag, auto
New in version 3.11: StrEnum, EnumCheck, ReprEnum, FlagBoundary, property, member, nonmember, global_enum, show_flag_values
———
Data Types
classenum.EnumType
EnumType is the
for enum enumerations. It is possible to subclass EnumType – see
for details.
EnumType is responsible for setting the correct __repr__(), __str__(), __format__(), and __reduce__() methods on the final enum, as well as creating the enum members, properly handling duplicates, providing iteration over the enum class, etc.
__call__(cls, value, names=None, *, module=None, qualname=None, type=None, start=1, boundary=None)
This method is called in two different ways:
to look up an existing member:
cls:The enum class being called.
value:The value to lookup.
to use the cls enum to create a new enum (only if the existing enum does not have any members):
cls:The enum class being called.
value:The name of the new Enum to create.
names:The names/values of the members for the new Enum.
module:The name of the module the new Enum is created in.
qualname:The actual location in the module where this Enum can be found.
type:A mix-in type for the new Enum.
start:The first integer value for the Enum (used by
).
boundary:How to handle out-of-range values from bit operations (
only).
__contains__(cls, member)
Returns True if member belongs to the cls:
>>> some_var=Color.RED>>> some_varinColorTrueNote
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)
Returns ['__class__','__doc__','__members__','__module__'] and the names of the members in cls:
>>> dir(Color)['BLUE', 'GREEN', 'RED', '__class__', '__contains__', '__doc__', '__getitem__', '__init_subclass__', '__iter__', '__len__', '__members__', '__module__', '__name__', '__qualname__']__getattr__(cls, name)
Returns the Enum member in cls matching name, or raises an
:
>>> Color.GREEN<Color.GREEN: 2>__getitem__(cls, name)
Returns the Enum member in cls matching name, or raises a
:
>>> 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>]New in version 3.11: Before 3.11 enum used EnumMeta type, which is kept as an alias.
classenum.Enum
Enum is the base class for all enum enumerations.
name
The name used to define the Enum member:
>>> Color.BLUE.name'BLUE'value
The value given to the Enum member:
>>> Color.RED.value1Value of the member, can be set in
.
Note
Enum member values
Member values can be anything:
,
, etc. If the exact value is unimportant you may use
instances and an appropriate value will be chosen for you. See
for the details.
While mutable/unhashable values, such as
,
or a mutable
, can be used, they will have a quadratic performance impact during creation relative to the total number of mutable/unhashable values in the enum.
_name_
Name of the member.
_value_
Value of the member, can be set in
.
_order_
No longer used, kept for backward compatibility. (class attribute, removed during class creation).
_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
for an example.
__dir__(self)
Returns ['__class__','__doc__','__module__','name','value'] and any public methods defined on self.__class__:
>>> fromdatetimeimportdate>>> classWeekday(Enum):... MONDAY=1... TUESDAY=2... WEDNESDAY=3... THURSDAY=4... FRIDAY=5... SATURDAY=6... SUNDAY=7... @classmethod... deftoday(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)
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
:
>>> fromenumimportauto>>> classPowersOfThree(Enum):... @staticmethod... def_generate_next_value_(name,start,count,last_values):... return3**(count+1)... FIRST=auto()... SECOND=auto()>>> PowersOfThree.SECOND.value9__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:
>>> fromenumimportStrEnum>>> classBuild(StrEnum):... DEBUG=auto()... OPTIMIZED=auto()... @classmethod... def_missing_(cls,value):... value=value.lower()... formemberincls:... ifmember.value==value:... returnmember... returnNone>>> 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:
>>> classOtherStyle(Enum):... ALTERNATE=auto()... OTHER=auto()... SOMETHING_ELSE=auto()... def__repr__(self):... cls_name=self.__class__.__name__... returnf'{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:
>>> classOtherStyle(Enum):... ALTERNATE=auto()... OTHER=auto()... SOMETHING_ELSE=auto()... def__str__(self):... returnf'{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
return value, but can be overridden:
>>> classOtherStyle(Enum):... ALTERNATE=auto()... OTHER=auto()... SOMETHING_ELSE=auto()... def__format__(self,spec):... returnf'{self.name}'>>> OtherStyle.ALTERNATE,str(OtherStyle.ALTERNATE),f"{OtherStyle.ALTERNATE}"(<OtherStyle.ALTERNATE: 1>, 'OtherStyle.ALTERNATE', 'ALTERNATE')Note
Using
with
results in integers of increasing value, starting with 1.
classenum.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.
>>> fromenumimportIntEnum>>> classNumber(IntEnum):... ONE=1... TWO=2... THREE=3...>>> Number.THREE<Number.THREE: 3>>>> Number.ONE+Number.TWO3>>> Number.THREE+58>>> Number.THREE==3TrueNote
Using
with
results in integers of increasing value, starting with 1.
Changed in version 3.11:
is now int.__str__() to better support the replacement of existing constants use-case.
was already int.__format__() for that same reason.
classenum.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
instead of a
subclass (i.e. type(unknown)==str instead of isinstance(unknown,str)), and in those locations you will need to use str(StrEnum.member).
Note
Using
with
results in the lower-cased member name as the value.
Note
is str.__str__() to better support the replacement of existing constants use-case.
is likewise str.__format__() for that same reason.
New in version 3.11.
classenum.Flag
Flag members support the bitwise operators & (AND), | (OR), ^ (XOR), and ~ (INVERT); the results of those operators are members of the enumeration.
__contains__(self, value)
Returns True if value is in self:
>>> fromenumimportFlag,auto>>> classColor(Flag):... RED=auto()... GREEN=auto()... BLUE=auto()>>> purple=Color.RED|Color.BLUE>>> white=Color.RED|Color.GREEN|Color.BLUE>>> Color.GREENinpurpleFalse>>> Color.GREENinwhiteTrue>>> purpleinwhiteTrue>>> whiteinpurpleFalse__iter__(self):Returns all contained non-alias members:
>>> list(Color.RED)[<Color.RED: 1>]>>> list(purple)[<Color.RED: 1>, <Color.BLUE: 4>]New in version 3.11.
__len__(self):Returns number of members in flag:
>>> len(Color.GREEN)1>>> len(white)3__bool__(self):Returns True if any members in flag, False otherwise:
>>> 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
and
.
Note
Using
with
results in integers that are powers of two, starting with 1.
Changed in version 3.11: The repr() of zero-valued flags has changed. It is now::
>>> Color(0)<Color: 0>classenum.IntFlag
IntFlag is the same as Flag, but its members are also integers and can be used anywhere that an integer can be used.
>>> fromenumimportIntFlag,auto>>> classColor(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+23If a Flag operation is performed with an IntFlag member and:
the result is a valid IntFlag: an IntFlag is returned
the result is not a valid IntFlag: the result depends on the FlagBoundary setting
The repr() of unnamed zero-valued flags has changed. It is now:
>>> Color(0)<Color: 0>Note
Using
with
results in integers that are powers of two, starting with 1.
Changed in version 3.11:
is now int.__str__() to better support the replacement of existing constants use-case.
was already int.__format__() for that same reason.
Inversion of an IntFlag now returns a positive value that is the union of all flags not in the given flag, rather than a negative value. This matches the existing
behavior.
classenum.ReprEnum
ReprEnum uses the
of
, but the
of the mixed-in data type:
int.__str__() for
and
str.__str__() for
Inherit from ReprEnum to keep the
/
of the mixed-in data type instead of using the
-default
.
New in version 3.11.
classenum.EnumCheck
EnumCheck contains the options used by the
decorator to ensure various constraints; failed constraints result in a
.
UNIQUE
Ensure that each value has only one name:
>>> fromenumimportEnum,verify,UNIQUE>>> @verify(UNIQUE)... classColor(Enum):... RED=1... GREEN=2... BLUE=3... CRIMSON=1Traceback (most recent call last):...ValueError: aliases found in <enum 'Color'>: CRIMSON -> REDCONTINUOUS
Ensure that there are no missing values between the lowest-valued member and the highest-valued member:
>>> fromenumimportEnum,verify,CONTINUOUS>>> @verify(CONTINUOUS)... classColor(Enum):... RED=1... GREEN=2... BLUE=5Traceback (most recent call last):...ValueError: invalid enum 'Color': missing values 3, 4NAMED_FLAGS
Ensure that any flag groups/masks contain only named flags – useful when values are specified instead of being generated by
:
>>> fromenumimportFlag,verify,NAMED_FLAGS>>> @verify(NAMED_FLAGS)... classColor(Flag):... RED=1... GREEN=2... BLUE=4... WHITE=15... NEON=31Traceback (most recent call last):...ValueError: invalid Flag 'Color': aliases WHITE and NEON are missing combined values of 0x18 [use enum.show_flag_values(value) for details]Note
CONTINUOUS and NAMED_FLAGS are designed to work with integer-valued members.
New in version 3.11.
classenum.FlagBoundary
FlagBoundary controls how out-of-range values are handled in Flag and its subclasses.
STRICT
Out-of-range values cause a
to be raised. This is the default for
:
>>> fromenumimportFlag,STRICT,auto>>> classStrictFlag(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 00111CONFORM
Out-of-range values have invalid values removed, leaving a valid Flag value:
>>> fromenumimportFlag,CONFORM,auto>>> classConformFlag(Flag,boundary=CONFORM):... RED=auto()... GREEN=auto()... BLUE=auto()>>> ConformFlag(2**2+2**4)<ConformFlag.BLUE: 4>EJECT
Out-of-range values lose their Flag membership and revert to
.
>>> fromenumimportFlag,EJECT,auto>>> classEjectFlag(Flag,boundary=EJECT):... RED=auto()... GREEN=auto()... BLUE=auto()>>> EjectFlag(2**2+2**4)20KEEP
Out-of-range values are kept, and the Flag membership is kept. This is the default for
:
>>> fromenumimportFlag,KEEP,auto>>> classKeepFlag(Flag,boundary=KEEP):... RED=auto()... GREEN=auto()... BLUE=auto()>>> KeepFlag(2**2+2**4)<KeepFlag.BLUE|16: 20>New in version 3.11.
———
Supported __dunder__ names
__members__ is a read-only ordered mapping of member_name:member items. It is only available on the class.
, 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.
Supported _sunder_ names
– name of the member
– value of the member; can be set in __new__
– a lookup function used when a value is not found; may be overridden
– a list of names, either as a
or a
, that will not be transformed into members, and will be removed from the final class
– no longer used, kept for backward compatibility (class attribute, removed during class creation)
– used to get an appropriate value for an enum member; may be overridden
Note
For standard
classes the next value chosen is the last value seen incremented by one.
For
classes the next value chosen will be the next highest power-of-two, regardless of the last value seen.
New in version 3.6: _missing_, _order_, _generate_next_value_
New in version 3.7: _ignore_
———
Utilities and Decorators
classenum.auto
auto can be used in place of a value. If used, the Enum machinery will call an Enum’s
to get an appropriate value. For Enum and IntEnum that appropriate value will be the last value plus one; for Flag and IntFlag it will be the first power-of-two greater than the highest value; for StrEnum it will be the lower-cased version of the member’s name. Care must be taken if mixing auto() with manually specified values.
auto instances are only resolved when at the top level of an assignment:
FIRST=auto() will work (auto() is replaced with 1);
SECOND=auto(),-2 will work (auto is replaced with 2, so 2,-2 is used to create the SECOND enum member;
THREE=[auto(),-3] will not work (<autoinstance>,-3 is used to create the THREE enum member)
Changed in version 3.11.1: In prior versions, auto() had to be the only thing on the assignment line to work properly.
_generate_next_value_ can be overridden to customize the values used by auto.
Note
in 3.13 the default _generate_next_value_ will always return the highest member value incremented by 1, and will fail if any member is an incompatible type.
@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.
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.
New in version 3.11.
@enum.unique
A
decorator specifically for enumerations. It searches an enumeration’s __members__, gathering any aliases it finds; if any are found
is raised with the details:
>>> fromenumimportEnum,unique>>> @unique... classMistake(Enum):... ONE=1... TWO=2... THREE=3... FOUR=3...Traceback (most recent call last):...ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> [email protected]
A
decorator specifically for enumerations. Members from
are used to specify which constraints should be checked on the decorated enumeration.
New in version 3.11.
@enum.member
A decorator for use in enums: its target will become a member.
New in version 3.11.
@enum.nonmember
A decorator for use in enums: its target will not become a member.
New in version 3.11.
@enum.global_enum
A decorator to change the
and
of an enum to show its members as belonging to the module instead of its class. Should only be used when the enum members are exported to the module global namespace (see
for an example).
New in version 3.11.
enum.show_flag_values(value)
Return a list of all power-of-two integers contained in a flag value.
New in version 3.11.
———
Notes
,
, and
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:
>>> fromenumimportEnum>>> classMyIntEnum(int,Enum):... passor you can reassign the appropriate
, etc., in your enum:
>>> fromenumimportEnum,IntEnum>>> classMyIntEnum(IntEnum):... __str__=Enum.__str__