[Tutor] Python Version of "enum" ?

Lloyd Kvam pythonTutor at venix.com
Fri Oct 22 00:03:15 CEST 2004

Enum is not built in to Python.  Here is my little Enum module.  Google
should turn up others.

class Enum(object):
    def __init__(self, codes):
        for ndx,code in enumerate(codes):
            setattr(self, code, ndx)
        self.length = len(codes)
        if '_codes' not in codes:
            self._codes = codes
    def __len__(self):
        return self.length

typically, usage works like so:

bulb = Enum("OFF,ON".split(','))
bulb.OFF == 0
bulb.ON == 1

It is usually most convenient to keep the Enum instance names fairly

Creating other variations from a list of strings is pretty easy. 
enumerate and setattr are the keys to making this work.  enumerate
numbers the names in a list.  setattr creates object attribute names on
the fly.  The main pitfall is that the Enum strings MUST be valid Python

On Thu, 2004-10-21 at 16:47, Gooch, John wrote:
> Is there an equivalent of C++'s 'enum' keyword to set a number of named
> constants ( like so ) 
> enum {
> 	OFF,
> 	ON,
> }; 
> in Python? It makes reading the code a lot simpler, as opposed to having to
> look up what a status of "1" means, it can be replaced with "ON", which is
> much easier to understand. 
> If not, can you declare named constants another way? Perhaps 'const MONDAY =
> 1', for example. 
> Thank You, 
> John A. Gooch
> Systems Administrator
> IT - Tools
> EchoStar Satellite L.L.C.
> 9601 S. Meridian Blvd.
> Englewood, CO  80112
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Lloyd Kvam
Venix Corp

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