Python: Enum枚举的实现
http://www.cnblogs.com/codingmylife/archive/2013/05/31/3110656.html
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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分类: Python
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