new enum idiom

[Jan Dries]

Jonathan Polley wrote:
> 
> Is is possible to modify the 'enum' function so that I don't have to provide a
> class?  I would like to use something like this method to create enumerated types,
> but I don't want to keep generating classes that say:
>
> I would like to just do a:
> 
> MIDI_Event = enum("NOTE_ON", "NOTE_OFF", 3, "POLYPHONIC_KEY_PRESSURE",
> "CONTROLLER_CHANGE")

I once wrote a class to simulate enums. Using it, you can write:

  colors = enum("GREEN","BLUE","RED","YELLOW")

and you can subsequently refer to the enum constants as:
  
  x = colors.GREEN

If no value is supplied, the first name is assigned 0, the second 1 and
so on. But you can supply values, as in:

  colors = enum("GREEN=1","BLUE=0x08","RED","YELLOW")

Anyway, here's the class:

import re

class enum:
    def __init__(self,*names):
        self.__mnames = {}
        value = 0;
        for i in names:
            pairs = re.split("\s*[=]\s*",i)
            if len(pairs) == 2:
                value = eval(pairs[1])
            self.__mnames[pairs[0]] = value
            value += 1
			
    def __getattr__(self,name):
        try:
            return self.__mnames[name]
        except:
            raise AttributeError
			
    def __setattr__(self,name,value):
        if name == "_enum__mnames":
            self.__dict__[name] = value
        else:
            raise AttributeError