从C#系语言过来用Python，好不容易适应了写代码不打花括号，突然有一天发现它居然木有枚举……于是stackoverflow了一把，发现神人的枚举（enum）实现到处都是，于是汉化总结过来。
如果是新版Python用户（Python 3.4 with PEP 435）：
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from
enum
import
Enum
Animal
=
Enum(
'Animal'
,
'ant bee cat dog'
)
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or
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class
Animals(Enum):
ant
=
1
bee
=
2
cat
=
3
dog
=
4
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旧版Python用户可以充分发挥动态语言的优越性来构造枚举，有简单的：
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def
enum(
*
*
enums):
return
type
(
'Enum'
, (), enums)
Numbers
=
enum(ONE
=
1
, TWO
=
2
, THREE
=
'three'
)
# Numbers.ONE == 1, Numbers.TWO == 2 and Numbers.THREE == 'three'
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有复杂的：
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def
enum(
*
sequential,
*
*
named):
enums
=
dict
(
zip
(sequential,
range
(
len
(sequential))),
*
*
named)
return
type
(
'Enum'
, (), enums)
Numbers
=
enum(
'ZERO'
,
'ONE'
,
'TWO'
)
# Numbers.ZERO == 0 and Numbers.ONE == 1
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有带值到名称映射的：
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def
enum(
*
sequential,
*
*
named):
enums
=
dict
(
zip
(sequential,
range
(
len
(sequential))),
*
*
named)
reverse
=
dict
((value, key)
for
key, value
in
enums.iteritems())
enums[
'reverse_mapping'
]
=
reverse
return
type
(
'Enum'
, (), enums)
# Numbers.reverse_mapping['three'] == 'THREE'
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有用set实现的：
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class
Enum(
set
):
def
__getattr__(
self
, name):
if
name
in
self
:
return
name
raise
AttributeError
Animals
=
Enum([
"DOG"
,
"CAT"
,
"HORSE"
])
print
Animals.DOG
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有用range实现的：
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dog, cat, rabbit
=
range
(
3
)
# or
class
Stationary:
(Pen, Pencil, Eraser)
=
range
(
0
,
3
)
print
Stationary.Pen
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有用tuple实现的：
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class
Enum(
tuple
): __getattr__
=
tuple
.index
State
=
Enum([
'Unclaimed'
,
'Claimed'
])
print
State.Claimed
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有用namedtuple实现的：
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from
collections
import
namedtuple
def
enum(
*
keys):
return
namedtuple(
'Enum'
, keys)(
*
keys)
MyEnum
=
enum(
'FOO'
,
'BAR'
,
'BAZ'
)
# 带字符数字映射的，像C/C++
def
enum(
*
keys):
return
namedtuple(
'Enum'
, keys)(
*
range
(
len
(keys)))
# 带字典映射的，可以映射出各种类型，不局限于数字
def
enum(
*
*
kwargs):
return
namedtuple(
'Enum'
, kwargs.keys())(
*
kwargs.values())
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