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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）： 1 2 | from enum import Enum
Animal = Enum('Animal', 'ant bee cat dog')
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or
1 2 3 4 5 | 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：
1 2 3 4 5 | 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：
1 2 3 4 5 6 | 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：
1 2 3 4 5 6 7 | 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：
1 2 3 4 5 6 7 8 | 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：
1 2 3 4 5 6 7 | 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：
1 2 3 4 | class Enum(tuple): __getattr__ = tuple.index
State = Enum(['Unclaimed', 'Claimed'])
print State.Claimed
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有用namedtuple实现的：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | 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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