Python: Enum枚举的实现

佚名 6年前 (2019-04-18) 随笔 1740人围观抢沙发百度已收录

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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1 2 3 4 5 class Animals(Enum): ant = 1 bee = 2 cat = 3 dog = 4

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'

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

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'

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

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

原文：http://www.cnblogs.com/codingmylife/archive/2013/05/31/3110656.html

有用tuple实现的：

1 2 3 4 class Enum( tuple ): __getattr__ = tuple .index State = Enum([ 'Unclaimed' , 'Claimed' ]) print State.Claimed

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())