带有属性的python枚举

Question

考虑:

class Item:
   def __init__(self, a, b):
       self.a = a
       self.b = b

class Items:
    GREEN = Item('a', 'b')
    BLUE = Item('c', 'd')

有没有办法让简单枚举的想法适应这种情况？(参见这个问题)理想情况下,就像在Java中一样,我想把它全部塞进一个类中.

Java模型:

enum EnumWithAttrs {
    GREEN("a", "b"),
    BLUE("c", "d");

    EnumWithAttrs(String a, String b) {
      this.a = a;
      this.b = b;
    }

    private String a;
    private String b;

    /* accessors and other java noise */
}

Answer 1

对于 Python 3：

class Status(Enum):
    READY = "ready", "I'm ready to do whatever is needed"
    ERROR = "error", "Something went wrong here"

    def __new__(cls, *args, **kwds):
        obj = object.__new__(cls)
        obj._value_ = args[0]
        return obj

    # ignore the first param since it's already set by __new__
    def __init__(self, _: str, description: str = None):
        self._description_ = description

    def __str__(self):
        return self.value

    # this makes sure that the description is read-only
    @property
    def description(self):
        return self._description_

您可以按类型将其用作标准枚举或工厂：

print(Status.READY)
# ready
print(Status.READY.description)
# I'm ready to do whatever is needed
print(Status("ready")) # this does not create a new object
# ready

Answer 2

Python 3.4有一个新的Enum数据类型(已经向后移植enum34并增强为aenum¹).两者enum34和aenum^2都轻松支持您的用例:

[ aenumpy2/3]

import aenum
class EnumWithAttrs(aenum.AutoNumberEnum):
    _init_ = 'a b'
    GREEN = 'a', 'b'
    BLUE = 'c', 'd'

[ enum34py2/3或stdlib enum3.4+]

import enum
class EnumWithAttrs(enum.Enum):

    def __new__(cls, *args, **kwds):
        value = len(cls.__members__) + 1
        obj = object.__new__(cls)
        obj._value_ = value
        return obj

    def __init__(self, a, b):
        self.a = a
        self.b = b

    GREEN = 'a', 'b'
    BLUE = 'c', 'd'

在使用中:

--> EnumWithAttrs.BLUE
<EnumWithAttrs.BLUE: 1>

--> EnumWithAttrs.BLUE.a
'c'

¹披露:我是Python stdlibEnum,enum34backport和Advanced Enumeration(aenum) 库的作者.

² aenum还支持NamedConstants基于元类和NamedTuples.

Answer 3

这是我认为比其他方法更简单的另一种方法，但具有最大的灵活性：

from collections import namedtuple
from enum import Enum

class Status(namedtuple('Status', 'name description'), Enum):
    READY = 'ready', 'I am ready to do whatever is needed'
    ERROR = 'error', 'Something went wrong here'

    def __str__(self) -> str:
        return self.name

按预期工作：

print(Status.READY)
print(repr(Status.READY))
print(Status.READY.description)
print(Status.READY.value)

印刷：

ready
<Status.READY: Status(name='ready', description='I am ready to do whatever is needed')>
I am ready to do whatever is needed
Status(name='ready', description='I am ready to do whatever is needed')

您可以充分利用namedtuple 和 Enum。

Answer 4

经过大量搜索后，我找到了这两个工作示例！

这就是我的朋友们！

代码...

from enum import Enum


class StatusInt(int, Enum):
    READY = (0, "Ready to go!")
    ERROR = (1, "Something wrong!")

    def __new__(cls, value, description):
        obj = int.__new__(cls, value)
        obj._value_ = value
        obj._description_ = description
        return obj

    @property
    def description(self):
        return self._description_


class StatusObj(Enum):
    READY = (0, "Ready to go!")
    ERROR = (1, "Something wrong!")

    def __init__(self, value, description):
        self._value_ = value
        self._description_ = description

    @property
    def description(self):
        return self._description_


print(str(StatusInt.READY == StatusInt.ERROR))
print(str(StatusInt.READY.value))
print(StatusInt.READY.description)

print(str(StatusObj.READY == StatusObj.ERROR))
print(str(StatusObj.READY.value))
print(StatusObj.READY.description)

输出...

False
0
Ready to go!
False
0
Ready to go!

[参考文献： https://docs.python.org/3/library/enum.html#when-to-use-new-vs-init，https://docs.python.org/3/library /enum.html#planet ]

Answer 5

使用namedtuple：

from collections import namedtuple

Item = namedtuple('abitem', ['a', 'b'])

class Items:
    GREEN = Item('a', 'b')
    BLUE = Item('c', 'd')