` and `repr` of an enum to show its members as belonging to the module instead of its class, and export the enum members to the global namespace.
>
> `show_flag_values`
>
> > Return a list of all power-of-two integers contained in a flag.
>
> `enum.bin`
>
> > Like built-in `bin`, except negative values are represented in two's complement, and the leading bit always indicates sign (`0` implies positive, `1` implies negative).
3.6 `Flag`, `IntFlag`, `auto`
3.11 `StrEnum`, `EnumCheck`, `ReprEnum`, `FlagBoundary`, `property`, `member`, `nonmember`, `global_enum`, `show_flag_values`
3.13 `EnumDict`
------------------------------------------------------------------------
## Data types
*EnumType* is the `metaclass` for *enum* enumerations. It is possible to subclass *EnumType* -- see `Subclassing EnumType
` 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.
3.11
Before 3.11 `EnumType` was called `EnumMeta`, which is still available as an alias.
EnumType.\_\_call\_\_(cls, value, names=None, \*, module=None, qualname=None, type=None, start=1, boundary=None)
This method is called in two different ways:
- to look up an existing member:
> cls
> The enum class being called.
>
> value
> The value to lookup.
- to use the `cls` enum to create a new enum (only if the existing enum does not have any members):
> cls
> The enum class being called.
>
> value
> The name of the new Enum to create.
>
> names
> The names/values of the members for the new Enum.
>
> module
> The name of the module the new Enum is created in.
>
> qualname
> The actual location in the module where this Enum can be found.
>
> type
> A mix-in type for the new Enum.
>
> start
> The first integer value for the Enum (used by `auto`).
>
> boundary
> How to handle out-of-range values from bit operations (`Flag` only).
EnumType.\_\_contains\_\_(cls, member)
Returns `True` if member belongs to the `cls`:
>>> some_var = Color.RED
>>> some_var in Color
True
>>> Color.RED.value in Color
True
3.12
Before Python 3.12, a `TypeError` is raised if a non-Enum-member is used in a containment check.
EnumType.\_\_dir\_\_(cls)
Returns `['__class__', '__doc__', '__members__', '__module__']` and the names of the members in *cls*:
>>> dir(Color)
['BLUE', 'GREEN', 'RED', '__class__', '__contains__', '__doc__', '__getitem__', '__init_subclass__', '__iter__', '__len__', '__members__', '__module__', '__name__', '__qualname__', '_generate_next_value_', '_missing_']
EnumType.\_\_getitem\_\_(cls, name)
Returns the Enum member in *cls* matching *name*, or raises a `KeyError`:
>>> Color['BLUE']
EnumType.\_\_iter\_\_(cls)
Returns each member in *cls* in definition order:
>>> list(Color)
[, , ]
EnumType.\_\_len\_\_(cls)
Returns the number of members in *cls*:
>>> len(Color)
3
EnumType.\_\_members\_\_
Returns a mapping of every enum name to its member, including aliases
EnumType.\_\_reversed\_\_(cls)
Returns each member in *cls* in reverse definition order:
>>> list(reversed(Color))
[, , ]
*Enum* is the base class for all *enum* enumerations.
Enum.name
The name used to define the `Enum` member:
>>> Color.BLUE.name
'BLUE'
Enum.value
The value given to the `Enum` member:
>>> Color.RED.value
1
Value of the member, can be set in `~Enum.__new__`.
> [!NOTE]
> Enum member values
>
> Member values can be anything: `int`, `str`, etc. If the exact value is unimportant you may use `auto` instances and an appropriate value will be chosen for you. See `auto` for the details.
>
> While mutable/unhashable values, such as `dict`, `list` or a mutable `~dataclasses.dataclass`, can be used, they will have a quadratic performance impact during creation relative to the total number of mutable/unhashable values in the enum.
Enum.\_name\_
Name of the member.
Enum.\_value\_
Value of the member, can be set in `~Enum.__new__`.
Enum.\_order\_
No longer used, kept for backward compatibility. (class attribute, removed during class creation).
The `~Enum._order_` attribute can be provided to help keep Python 2 / Python 3 code in sync. It will be checked against the actual order of the enumeration and raise an error if the two do not match:
>>> class Color(Enum):
... _order_ = 'RED GREEN BLUE'
... RED = 1
... BLUE = 3
... GREEN = 2
...
Traceback (most recent call last):
...
TypeError: member order does not match _order_:
['RED', 'BLUE', 'GREEN']
['RED', 'GREEN', 'BLUE']
> [!NOTE]
> In Python 2 code the `~Enum._order_` attribute is necessary as definition order is lost before it can be recorded.
3.6
Enum.\_ignore\_
`_ignore_` is only used during creation and is removed from the enumeration once creation is complete.
`_ignore_` is a list of names that will not become members, and whose names will also be removed from the completed enumeration. See `TimePeriod
` for an example.
3.7
Enum.\_\_dir\_\_(self)
Returns `['__class__', '__doc__', '__module__', 'name', 'value']` and any public methods defined on *self.\_\_class\_\_*:
>>> from enum import Enum
>>> import datetime as dt
>>> class Weekday(Enum):
... MONDAY = 1
... TUESDAY = 2
... WEDNESDAY = 3
... THURSDAY = 4
... FRIDAY = 5
... SATURDAY = 6
... SUNDAY = 7
... @classmethod
... def today(cls):
... print(f'today is {cls(dt.date.today().isoweekday()).name}')
...
>>> dir(Weekday.SATURDAY)
['__class__', '__doc__', '__eq__', '__hash__', '__module__', '_add_alias_', '_add_value_alias_', '_generate_next_value_', '_missing_', 'name', 'today', 'value']
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 `auto`.
> [!NOTE]
For standard `Enum` classes the next value chosen is the highest value seen incremented by one.
For `Flag` classes the next value chosen will be the next highest power-of-two.
This method may be overridden, e.g.:
>>> from enum import auto, Enum
>>> class PowersOfThree(Enum):
... @staticmethod ... def
generate_next_value\_(name, start, count, last_values): ... return 3 \*\* (count + 1) ... FIRST = auto() ... SECOND = auto() ... \>\>\> PowersOfThree.SECOND.value 9
3.6
3.13
Prior versions would use the last seen value instead of the highest value.
Enum.\_\_init\_\_(self, *args,*\*kwds)
By default, does nothing. If multiple values are given in the member assignment, those values become separate arguments to `__init__`; e.g.
> \>\>\> from enum import Enum \>\>\> class Weekday(Enum): ... MONDAY = 1, 'Mon'
`Weekday.__init__()` would be called as `Weekday.__init__(self, 1, 'Mon')`
Enum.\_\_init_subclass\_\_(cls, \*\*kwds)
A *classmethod* that is used to further configure subsequent subclasses. By default, does nothing.
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 auto, 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')
3.6
Enum.\_\_new\_\_(cls, *args,*\*kwds)
By default, doesn't exist. If specified, either in the enum class definition or in a mixin class (such as `int`), all values given in the member assignment will be passed; e.g.
> \>\>\> from enum import Enum \>\>\> class MyIntEnum(int, Enum): ... TWENTYSIX = '1a', 16
results in the call `int('1a', 16)` and a value of `26` for the member.
> [!NOTE]
> When writing a custom `__new__`, do not use `super().__new__` -- call the appropriate `__new__` instead.
Enum.\_\_repr\_\_(self)
Returns the string used for *repr()* calls. By default, returns the *Enum* name, member name, and value, but can be overridden:
>>> from enum import auto, Enum
>>> 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')
Enum.\_\_str\_\_(self)
Returns the string used for *str()* calls. By default, returns the *Enum* name and member name, but can be overridden:
>>> from enum import auto, Enum
>>> 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}"
(, 'ALTERNATE', 'ALTERNATE')
Enum.\_\_format\_\_(self)
Returns the string used for *format()* and *f-string* calls. By default, returns `__str__` return value, but can be overridden:
>>> from enum import auto, Enum
>>> 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', 'ALTERNATE')
> [!NOTE]
> Using `auto` with `Enum` results in integers of increasing value, starting with `1`.
3.12 Added `enum-dataclass-support`.
Enum.\_add_alias\_
Adds a new name as an alias to an existing member:
>>> Color.RED._add_alias_("ERROR")
>>> Color.ERROR
Raises a `NameError` if the name is already assigned to a different member.
3.13
Enum.\_add_value_alias\_
Adds a new value as an alias to an existing member:
>>> Color.RED._add_value_alias_(42)
>>> Color(42)
Raises a `ValueError` if the value is already linked with a different member.\
See `multi-value-enum` for an example.
3.13
*IntEnum* is the same as `Enum`, but its members are also integers and can be used anywhere that an integer can be used. If any integer operation is performed with an *IntEnum* member, the resulting value loses its enumeration status.
> \>\>\> from enum import IntEnum \>\>\> class Number(IntEnum): ... ONE = 1 ... TWO = 2 ... THREE = 3 ... \>\>\> Number.THREE \
\>\>\> Number.ONE + Number.TWO 3 \>\>\> Number.THREE + 5 8 \>\>\> Number.THREE == 3 True
> [!NOTE]
> Using `auto` with `IntEnum` results in integers of increasing value, starting with `1`.
3.11 `~object.__str__` is now `!int.__str__` to better support the *replacement of existing constants* use-case. `~object.__format__` was already `!int.__format__` for that same reason.
*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.
\>\>\> from enum import StrEnum, auto \>\>\> class Color(StrEnum): ... RED = 'r' ... GREEN = 'g' ... BLUE = 'b' ... UNKNOWN = auto() ... \>\>\> Color.RED \
\>\>\> Color.UNKNOWN \ \>\>\> str(Color.UNKNOWN) 'unknown'
> [!NOTE]
> There are places in the stdlib that check for an exact `str` instead of a `str` subclass (i.e. `type(unknown) == str` instead of `isinstance(unknown, str)`), and in those locations you will need to use `str(MyStrEnum.MY_MEMBER)`.
> [!NOTE]
> Using `auto` with `StrEnum` results in the lower-cased member name as the value.
> [!NOTE]
> `~object.__str__` is `!str.__str__` to better support the *replacement of existing constants* use-case. `~object.__format__` is likewise `!str.__format__` for that same reason.
3.11
`Flag` is the same as `Enum`, but its members support the bitwise operators `&` (*AND*), `|` (*OR*), `^` (*XOR*), and `~` (*INVERT*); the results of those operations are (aliases of) members of the enumeration.
\_\_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
\_\_iter\_\_(self)
Returns all contained non-alias members:
>>> list(Color.RED)
[
]
>>> list(purple)
[, ]
3.11
\_\_len\_\_(self)
Returns number of members in flag:
>>> len(Color.GREEN)
1
>>> len(white)
3
3.11
\_\_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
\_\_and\_\_(self, other)
Returns current flag binary and'ed with other:
>>> purple & white
>>> purple & Color.GREEN
\_\_xor\_\_(self, other)
Returns current flag binary xor'ed with other:
>>> purple ^ white
>>> purple ^ Color.GREEN
\_\_invert\_\_(self)
Returns all the flags in *type(self)* that are not in *self*:
>>> ~white
>>> ~purple
>>> ~Color.RED
numeric_repr\_
Function used to format any remaining unnamed numeric values. Default is the value's repr; common choices are `hex` and `oct`.
> [!NOTE]
> Using `auto` with `Flag` results in integers that are powers of two, starting with `1`.
3.11 The *repr()* of zero-valued flags has changed. It is now:
\>\>\> Color(0) \# doctest: +SKIP \
`IntFlag` is the same as `Flag`, but its members are also integers and can be used anywhere that an integer can be used.
> \>\>\> from enum import IntFlag, auto \>\>\> class Color(IntFlag): ... RED = auto() ... GREEN = auto() ... BLUE = auto() ... \>\>\> Color.RED & 2 \
\>\>\> Color.RED \| 2 \
If any integer operation is performed with an *IntFlag* member, the result is not an *IntFlag*:
>>> Color.RED + 2
3
If a `Flag` operation is performed with an *IntFlag* member and:
- the result is a valid *IntFlag*: an *IntFlag* is returned
- the result is not a valid *IntFlag*: the result depends on the `FlagBoundary` setting
The `repr` of unnamed zero-valued flags has changed. It is now:
>>> Color(0)
> [!NOTE]
> Using `auto` with `IntFlag` results in integers that are powers of two, starting with `1`.
3.11
`~object.__str__` is now `!int.__str__` to better support the *replacement of existing constants* use-case. `~object.__format__` 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 `Flag` behavior.
`!ReprEnum` uses the `repr()
` of `Enum`, but the `str() ` of the mixed-in data type:
- `!int.__str__` for `IntEnum` and `IntFlag`
- `!str.__str__` for `StrEnum`
Inherit from `!ReprEnum` to keep the `str() ` / `format` of the mixed-in data type instead of using the `Enum`-default `str() `.
3.11
*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 : 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]
> [!NOTE]
> CONTINUOUS and NAMED_FLAGS are designed to work with integer-valued members.
3.11
`FlagBoundary` controls how out-of-range values are handled in `Flag` 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, auto
>>> class StrictFlag(Flag, boundary=STRICT):
... RED = auto()
... GREEN = auto()
... BLUE = auto()
...
>>> StrictFlag(2**2 + 2**4)
Traceback (most recent call last):
...
ValueError: invalid value 20
given 0b0 10100
allowed 0b0 00111
CONFORM
Out-of-range values have invalid values removed, leaving a valid `Flag` value:
>>> from enum import Flag, CONFORM, auto
>>> class ConformFlag(Flag, boundary=CONFORM):
... RED = auto()
... GREEN = auto()
... BLUE = auto()
...
>>> ConformFlag(2**2 + 2**4)
EJECT
Out-of-range values lose their `Flag` membership and revert to `int`.
> \>\>\> from enum import Flag, EJECT, auto \>\>\> 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 `Flag` membership is kept. This is the default for `IntFlag`:
>>> from enum import Flag, KEEP, auto
>>> class KeepFlag(Flag, boundary=KEEP):
... RED = auto()
... GREEN = auto()
... BLUE = auto()
...
>>> KeepFlag(2**2 + 2**4)
3.11
*EnumDict* is a subclass of `dict` that is used as the namespace for defining enum classes (see `prepare`). It is exposed to allow subclasses of `EnumType` with advanced behavior like having multiple values per member. It should be called with the name of the enum class being created, otherwise private names and internal classes will not be handled correctly.
Note that only the `~collections.abc.MutableMapping` interface (`~object.__setitem__` and `~dict.update`) is overridden. It may be possible to bypass the checks using other `!dict` operations like `|=
`.
EnumDict.member_names
A list of member names.
3.13
3.6 `_missing_`, `_order_`, `_generate_next_value_`
3.7 `_ignore_`
3.13 `_add_alias_`, `_add_value_alias_`, `_repr_*`
------------------------------------------------------------------------
## Utilities and decorators
*auto* can be used in place of a value. If used, the *Enum* machinery will call an `Enum`'s `~Enum._generate_next_value_` to get an appropriate value. For `Enum` and `IntEnum` that appropriate value will be the highest value seen plus one; for `Flag` and `IntFlag` it will be the first power-of-two greater than the highest value seen; 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, either by itself or as part of a tuple:
- `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;
- `THIRD = [auto(), -3]` will *not* work (`[
, -3]` is used to create the `THIRD` enum member)
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 version 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.
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`.
3.11
unique
A `class` decorator specifically for enumerations. It searches an enumeration's `~EnumType.__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 : FOUR -> THREE
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
member
A decorator for use in enums: its target will become a member.
3.11
nonmember
A decorator for use in enums: its target will not become a member.
3.11
global_enum
A decorator to change the `str()
` and `repr` of an enum to show its members as belonging to the module instead of its class. Should only be used when the enum members are exported to the module global namespace (see `re.RegexFlag` for an example).
3.11
show_flag_values(value)
Return a list of all power-of-two integers contained in a flag *value*.
3.11
bin(num, max_bits=None)
Like built-in `bin`, except negative values are represented in two's complement, and the leading bit always indicates sign (`0` implies positive, `1` implies negative).
> \>\>\> import enum \>\>\> enum.bin(10) '0b0 1010' \>\>\> enum.bin(~10) \# ~10 is -11 '0b1 0101'
3.11