将枚举成员的值自动设置为其名称 [英] Automatically setting an enum member's value to its name
问题描述
class Color(AutoNumber):
red =()
green = )
...
我想做一个类似的类,但是值会自动从成员的名称设置,并保持您从 str
和枚举获得的功能
mixin stuff
所以类似:
class Animal(MagicStrEnum):
horse =()
dog =()
Animal.dog =='dog'#True
我看了在枚举模块的源代码中,尝试了很多变体,它们围绕着 __ new __
和 EnumMeta
class
更新:2017-03-01
在Python 3.6(和
Aenum 2.0
1 )标记
和IntFlag
类已添加;其中一部分是新的auto( )
帮助器,这使得这很简单:
>>> class AutoName(Enum):
... def _generate_next_value_(name,start,count,last_values):
...返回名称
...
>> ; class Ordinal(AutoName):
... NORTH = auto()
... SOUTH = auto()
... EAST = auto()
... WEST = auto()
...
>>> list(Ordinal)
[< Ordinal.NORTH:'NORTH'>,< Ordinal.SOUTH:'SOUTH'>,< Ordinal.EAST:'EAST'>,< Ordinal.WEST :'WEST'>]
原始答案
使用 AutoStr
类的难点是枚举成员的名称不是传入创建它的代码,所以它不可用。另一个皱纹是 str
是不可变的,所以我们不能在创建枚举后改变这些类型的枚举(通过使用 class decorator )。
最简单的做法是使用功能API :
Animal = Enum('Animal',[(a,a)for a('horse','dog')],type = str)
这给了我们:
>>> list(Animal)
[< Animal.horse:'horse'>,< Animal.dog:'dog'>]
>>> Animal.dog =='dog'
True
下一个最简单的事情,假设你想为你今后的枚举使用一个基类,就像我的 DocEnem
:
class DocEnum(Enum):
比较相当于其名称的所有封装版本
接受
def __new __(cls,* args):
忽略参数(将在__init__中处理)
obj =对象.__新__(cls)
obj._value_ =无
返回obj
def __init __(self,doc = None):
#first,fix _value_
self._value_ = self._name_.lower()
self .__ doc__ = doc
def __eq __(self,other):
if isinstance(other,basestring):
return self._value_ == other.lower()
elif not isinstance(other,self .__ class__):
return NotImplement ed
return self is other
def __ne __(self,other):
return not self == other
并正在使用:
class SpecKind(DocEnum):
REQUIRED =required value
OPTION =每个名称的单个值
MULTI =每个名称的多个值(列表形式)
FLAG =每个名称的布尔值
KEYWORD ='未知选项'
请注意,与第一个选项不同, DocEnum
成员不是 str
s。
如果你想做的很难的方式:子类 EnumMeta
并提出新的枚举
的类字典之前的成员被创建:
从枚举导入EnumMeta, enum,_EnumDict
class StrEnumMeta(EnumMeta):
def __new __(metacls,cls,bases,oldclassdict):
扫描oldclassdict和合作将任何一个简单元组
的值转换为名称中的str,而不是
newclassdict = _EnumDict()
for k,v in oldclassdict.items )
如果v ==():
v = k
newclassdict [k] = v
return super().__ new __(metacls,cls,bases,newclassdict)
class AutoStrEnum(str,Enum,metaclass = StrEnumMeta):
name = value str enums的基类
class Animal(AutoStrEnum):
马=()
dog =()
whale =()
print(Animal.horse)
print(Animal.horse =='horse')
print(Animal.horse.name,Animal.horse.value)
哪个给我们:
Animal.horse
/ pre>
True
马马
1 披露:我是 Python stdlib
枚举
,enum34
backport 和高级枚举(aenum
)库。I've been messing around with python's enum library and have come across a conundrum. In the docs, they show an example of an auto-numbering enum, wherein something is defined:
class Color(AutoNumber): red = () green = () ...
I want to make a similar class, but the value would automatically be set from the name of the member AND keep the functionality that you get from doing the
str
andenum
mixin stuffSo something like:
class Animal(MagicStrEnum): horse = () dog = () Animal.dog == 'dog' # True
I've looked at the source code of the enum module and tried a lot of variations messing around with
__new__
and theEnumMeta
class解决方案Update: 2017-03-01
In Python 3.6 (and
Aenum 2.0
1)Flag
andIntFlag
classes have been added; part of that was a newauto()
helper that makes this trivially easy:
>>> class AutoName(Enum): ... def _generate_next_value_(name, start, count, last_values): ... return name ... >>> class Ordinal(AutoName): ... NORTH = auto() ... SOUTH = auto() ... EAST = auto() ... WEST = auto() ... >>> list(Ordinal) [<Ordinal.NORTH: 'NORTH'>, <Ordinal.SOUTH: 'SOUTH'>, <Ordinal.EAST: 'EAST'>, <Ordinal.WEST: 'WEST'>]
Original answer
The difficulty with an
AutoStr
class is that the name of the enum member is not passed into the code that creates it, so it is unavailable for use. Another wrinkle is thatstr
is immutable, so we can't change those types of enums after they have been created (by using a class decorator, for example).The easiest thing to do is use the Functional API:
Animal = Enum('Animal', [(a, a) for a in ('horse', 'dog')], type=str)
which gives us:
>>> list(Animal) [<Animal.horse: 'horse'>, <Animal.dog: 'dog'>] >>> Animal.dog == 'dog' True
The next easiest thing to do, assuming you want to make a base class for your future enumeration use, would be something like my
DocEnem
:class DocEnum(Enum): """ compares equal to all cased versions of its name accepts a doctring for each member """ def __new__(cls, *args): """Ignores arguments (will be handled in __init__)""" obj = object.__new__(cls) obj._value_ = None return obj def __init__(self, doc=None): # first, fix _value_ self._value_ = self._name_.lower() self.__doc__ = doc def __eq__(self, other): if isinstance(other, basestring): return self._value_ == other.lower() elif not isinstance(other, self.__class__): return NotImplemented return self is other def __ne__(self, other): return not self == other
and in use:
class SpecKind(DocEnum): REQUIRED = "required value" OPTION = "single value per name" MULTI = "multiple values per name (list form)" FLAG = "boolean value per name" KEYWORD = 'unknown options'
Note that unlike the first option,
DocEnum
members are notstr
s.
If you want to do it the hard way: subclass
EnumMeta
and fiddle with the newEnum
's class dictionary before the members are created:from enum import EnumMeta, Enum, _EnumDict class StrEnumMeta(EnumMeta): def __new__(metacls, cls, bases, oldclassdict): """ Scan through `oldclassdict` and convert any value that is a plain tuple into a `str` of the name instead """ newclassdict = _EnumDict() for k, v in oldclassdict.items(): if v == (): v = k newclassdict[k] = v return super().__new__(metacls, cls, bases, newclassdict) class AutoStrEnum(str, Enum, metaclass=StrEnumMeta): "base class for name=value str enums" class Animal(AutoStrEnum): horse = () dog = () whale = () print(Animal.horse) print(Animal.horse == 'horse') print(Animal.horse.name, Animal.horse.value)
Which gives us:
Animal.horse True horse horse
1 Disclosure: I am the author of the Python stdlib
Enum
, theenum34
backport, and the Advanced Enumeration (aenum
) library.这篇关于将枚举成员的值自动设置为其名称的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!