我喜欢Java枚举，这就是我在Python中的做法:

def enum(clsdef):
    class Enum(object):
        __slots__=tuple([var for var in clsdef.__dict__ if isinstance((getattr(clsdef, var)), tuple) and not var.startswith('__')])

        def __new__(cls, *args, **kwargs):
            if not '_the_instance' in cls.__dict__:
                cls._the_instance = object.__new__(cls, *args, **kwargs)
            return cls._the_instance

        def __init__(self):
            clsdef.values=lambda cls, e=Enum: e.values()
            clsdef.valueOf=lambda cls, n, e=self: e.valueOf(n)
            for ordinal, key in enumerate(self.__class__.__slots__):
                args=getattr(clsdef, key)
                instance=clsdef(*args)
                instance._name=key
                instance._ordinal=ordinal
                setattr(self, key, instance)

        @classmethod
        def values(cls):
            if not hasattr(cls, '_values'):
                cls._values=[getattr(cls, name) for name in cls.__slots__]
            return cls._values

        def valueOf(self, name):
            return getattr(self, name)

        def __repr__(self):
            return ''.join(['<class Enum (', clsdef.__name__, ') at ', str(hex(id(self))), '>'])

    return Enum()

示例使用:

i=2
@enum
class Test(object):
    A=("a",1)
    B=("b",)
    C=("c",2)
    D=tuple()
    E=("e",3)

    while True:
        try:
            F, G, H, I, J, K, L, M, N, O=[tuple() for _ in range(i)]
            break;
        except ValueError:
            i+=1

    def __init__(self, name="default", aparam=0):
        self.name=name
        self.avalue=aparam

所有类变量都定义为元组，就像构造函数一样。到目前为止，还不能使用命名参数。

在Java pre-JDK 5中使用的类型安全枚举模式有一个 优势的数量。就像Alexandru的回答一样，你创建了一个 类和类级别字段是枚举值;然而，枚举 值是类的实例，而不是小整数。这已经 优点是枚举值不会在不经意间比较相等 对于小整数，你可以控制它们的打印方式，任意添加 方法(如果有用的话)，并使用isinstance进行断言:

class Animal:
   def __init__(self, name):
       self.name = name

   def __str__(self):
       return self.name

   def __repr__(self):
       return "<Animal: %s>" % self

Animal.DOG = Animal("dog")
Animal.CAT = Animal("cat")

>>> x = Animal.DOG
>>> x
<Animal: dog>
>>> x == 1
False

python-dev上最近的一个线程指出，在野外有几个枚举库，包括:

flufl.enum lazr.enum ．.． 和富有想象力的enum

这是我见过的最好的一个:“Python中的First Class Enums”

http://code.activestate.com/recipes/413486/

It gives you a class, and the class contains all the enums. The enums can be compared to each other, but don't have any particular value; you can't use them as an integer value. (I resisted this at first because I am used to C enums, which are integer values. But if you can't use it as an integer, you can't use it as an integer by mistake so overall I think it is a win.) Each enum is a unique value. You can print enums, you can iterate over them, you can test that an enum value is "in" the enum. It's pretty complete and slick.

编辑(cfi):上面的链接不兼容Python 3。下面是我将枚举.py移植到Python 3的端口:

def cmp(a,b):
   if a < b: return -1
   if b < a: return 1
   return 0


def Enum(*names):
   ##assert names, "Empty enums are not supported" # <- Don't like empty enums? Uncomment!

   class EnumClass(object):
      __slots__ = names
      def __iter__(self):        return iter(constants)
      def __len__(self):         return len(constants)
      def __getitem__(self, i):  return constants[i]
      def __repr__(self):        return 'Enum' + str(names)
      def __str__(self):         return 'enum ' + str(constants)

   class EnumValue(object):
      __slots__ = ('__value')
      def __init__(self, value): self.__value = value
      Value = property(lambda self: self.__value)
      EnumType = property(lambda self: EnumType)
      def __hash__(self):        return hash(self.__value)
      def __cmp__(self, other):
         # C fans might want to remove the following assertion
         # to make all enums comparable by ordinal value {;))
         assert self.EnumType is other.EnumType, "Only values from the same enum are comparable"
         return cmp(self.__value, other.__value)
      def __lt__(self, other):   return self.__cmp__(other) < 0
      def __eq__(self, other):   return self.__cmp__(other) == 0
      def __invert__(self):      return constants[maximum - self.__value]
      def __nonzero__(self):     return bool(self.__value)
      def __repr__(self):        return str(names[self.__value])

   maximum = len(names) - 1
   constants = [None] * len(names)
   for i, each in enumerate(names):
      val = EnumValue(i)
      setattr(EnumClass, each, val)
      constants[i] = val
   constants = tuple(constants)
   EnumType = EnumClass()
   return EnumType


if __name__ == '__main__':
   print( '\n*** Enum Demo ***')
   print( '--- Days of week ---')
   Days = Enum('Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa', 'Su')
   print( Days)
   print( Days.Mo)
   print( Days.Fr)
   print( Days.Mo < Days.Fr)
   print( list(Days))
   for each in Days:
      print( 'Day:', each)
   print( '--- Yes/No ---')
   Confirmation = Enum('No', 'Yes')
   answer = Confirmation.No
   print( 'Your answer is not', ~answer)

我喜欢在Python中这样定义枚举:

class Animal:
  class Dog: pass
  class Cat: pass

x = Animal.Dog

这比使用整数更有漏洞，因为你不必担心确保整数是唯一的(例如，如果你说Dog = 1和Cat = 1，你就完蛋了)。

它比使用字符串更防bug，因为你不必担心拼写错误(例如。 x == "猫"无声失败，但x ==动物。Catt是一个运行时异常)。

附录: 你甚至可以通过让Dog和Cat继承一个具有正确元类的符号类来增强这个解决方案:

class SymbolClass(type):
    def __repr__(self): return self.__qualname__
    def __str__(self): return self.__name__

class Symbol(metaclass=SymbolClass): pass


class Animal:
    class Dog(Symbol): pass
    class Cat(Symbol): pass

然后，如果你使用这些值来索引一个字典，请求它的表示将使它们看起来很漂亮:

>>> mydict = {Animal.Dog: 'Wan Wan', Animal.Cat: 'Nyaa'}
>>> mydict
{Animal.Dog: 'Wan Wan', Animal.Cat: 'Nyaa'}

有趣的是，前几天我正好需要这个，但我找不到一个值得使用的实现……所以我自己写了:

import functools

class EnumValue(object):
    def __init__(self,name,value,type):
        self.__value=value
        self.__name=name
        self.Type=type
    def __str__(self):
        return self.__name
    def __repr__(self):#2.6 only... so change to what ever you need...
        return '{cls}({0!r},{1!r},{2})'.format(self.__name,self.__value,self.Type.__name__,cls=type(self).__name__)

    def __hash__(self):
        return hash(self.__value)
    def __nonzero__(self):
        return bool(self.__value)
    def __cmp__(self,other):
        if isinstance(other,EnumValue):
            return cmp(self.__value,other.__value)
        else:
            return cmp(self.__value,other)#hopefully their the same type... but who cares?
    def __or__(self,other):
        if other is None:
            return self
        elif type(self) is not type(other):
            raise TypeError()
        return EnumValue('{0.Name} | {1.Name}'.format(self,other),self.Value|other.Value,self.Type)
    def __and__(self,other):
        if other is None:
            return self
        elif type(self) is not type(other):
            raise TypeError()
        return EnumValue('{0.Name} & {1.Name}'.format(self,other),self.Value&other.Value,self.Type)
    def __contains__(self,other):
        if self.Value==other.Value:
            return True
        return bool(self&other)
    def __invert__(self):
        enumerables=self.Type.__enumerables__
        return functools.reduce(EnumValue.__or__,(enum for enum in enumerables.itervalues() if enum not in self))

    @property
    def Name(self):
        return self.__name

    @property
    def Value(self):
        return self.__value

class EnumMeta(type):
    @staticmethod
    def __addToReverseLookup(rev,value,newKeys,nextIter,force=True):
        if value in rev:
            forced,items=rev.get(value,(force,()) )
            if forced and force: #value was forced, so just append
                rev[value]=(True,items+newKeys)
            elif not forced:#move it to a new spot
                next=nextIter.next()
                EnumMeta.__addToReverseLookup(rev,next,items,nextIter,False)
                rev[value]=(force,newKeys)
            else: #not forcing this value
                next = nextIter.next()
                EnumMeta.__addToReverseLookup(rev,next,newKeys,nextIter,False)
                rev[value]=(force,newKeys)
        else:#set it and forget it
            rev[value]=(force,newKeys)
        return value

    def __init__(cls,name,bases,atts):
        classVars=vars(cls)
        enums = classVars.get('__enumerables__',None)
        nextIter = getattr(cls,'__nextitr__',itertools.count)()
        reverseLookup={}
        values={}

        if enums is not None:
            #build reverse lookup
            for item in enums:
                if isinstance(item,(tuple,list)):
                    items=list(item)
                    value=items.pop()
                    EnumMeta.__addToReverseLookup(reverseLookup,value,tuple(map(str,items)),nextIter)
                else:
                    value=nextIter.next()
                    value=EnumMeta.__addToReverseLookup(reverseLookup,value,(str(item),),nextIter,False)#add it to the reverse lookup, but don't force it to that value

            #build values and clean up reverse lookup
            for value,fkeys in reverseLookup.iteritems():
                f,keys=fkeys
                for key in keys:
                    enum=EnumValue(key,value,cls)
                    setattr(cls,key,enum)
                    values[key]=enum
                reverseLookup[value]=tuple(val for val in values.itervalues() if val.Value == value)
        setattr(cls,'__reverseLookup__',reverseLookup)
        setattr(cls,'__enumerables__',values)
        setattr(cls,'_Max',max([key for key in reverseLookup] or [0]))
        return super(EnumMeta,cls).__init__(name,bases,atts)

    def __iter__(cls):
        for enum in cls.__enumerables__.itervalues():
            yield enum
    def GetEnumByName(cls,name):
        return cls.__enumerables__.get(name,None)
    def GetEnumByValue(cls,value):
        return cls.__reverseLookup__.get(value,(None,))[0]

class Enum(object):
    __metaclass__=EnumMeta
    __enumerables__=None

class FlagEnum(Enum):
    @staticmethod
    def __nextitr__():
        yield 0
        for val in itertools.count():
            yield 2**val

def enum(name,*args):
    return EnumMeta(name,(Enum,),dict(__enumerables__=args))

接受或离开它，它做了我需要它做的:)

像这样使用它:

class Air(FlagEnum):
    __enumerables__=('None','Oxygen','Nitrogen','Hydrogen')

class Mammals(Enum):
    __enumerables__=('Bat','Whale',('Dog','Puppy',1),'Cat')
Bool = enum('Bool','Yes',('No',0))

这个解决方案是获取定义为列表的枚举类的简单方法(没有更多烦人的整数赋值):

enumeration.py:

import new

def create(class_name, names):
    return new.classobj(
        class_name, (object,), dict((y, x) for x, y in enumerate(names))
    )

example.py:

import enumeration

Colors = enumeration.create('Colors', (
    'red',
    'orange',
    'yellow',
    'green',
    'blue',
    'violet',
))