Using Enums in Python

Examples

See - http://stackoverflow.com/questions/36932/whats-the-best-way-to-implement-an-enum-in-python

Here are a few of these...

One

class Animal:
    DOG=1
    CAT=2

x = Animal.DOG

Two

def enum(**enums):
    return type('Enum', (), enums)

Used like so:

>>> Numbers = enum(ONE=1, TWO=2, THREE='three')
>>> Numbers.ONE
1
>>> Numbers.TWO
2
>>> Numbers.THREE
'three'

Three

Provide automatic enumeration with something like this:

def enum(*sequential, **named):
    enums = dict(zip(sequential, range(len(sequential))), **named)
    return type('Enum', (), enums)

Used like so:

>>> Numbers = enum('ZERO', 'ONE', 'TWO')
>>> Numbers.ZERO
0
>>> Numbers.ONE
1

Four

class Enum(set):
    def __getattr__(self, name):
        if name in self:
            return name
        raise AttributeError

...

Animals = Enum(["DOG", "CAT", "Horse"])

print Animals.DOG

This can be further improved by overriding __setattr__(self, name, value) and maybe __delattr__(self, name) so that if you accidentally write Animals.DOG = CAT, it won't silently succeed.

Five

dog, cat, rabbit = range(3)

Five

class Animal:
   def __init__(self, name):
       self.name = name

   def __str__(self):
       return self.name

   def __repr__(self):
       return "<Animal: %s>" % self

Animal.DOG = Animal("dog")
Animal.CAT = Animal("cat")

>>> x = Animal.DOG
>>> x
<Animal: dog>
>>> x == 1
False