DRY functions with named attributes used as default arguments

[Tim Chase]

My intent is to have a function object something like

   def foo(arg1, arg2=foo.DEFAULT):
     return int(do_stuff(arg1, arg2))
   foo.SPECIAL = 42
   foo.MONKEY = 31415
   foo.DEFAULT = foo.SPECIAL

so I can call it with either

   result = foo(myarg)

or

   result = foo(myarg, foo.SPECIAL)

However I can't do this because foo.DEFAULT isn't defined at the 
time the function is created.  I'd like to avoid hard-coding 
things while staying DRY, so I don't like

   def foo(arg1, arg2=42)

because the default might change due to business rule changes, I 
have a dangling "magic constant" and if the value of SPECIAL 
changes, I have to catch that it should be changed in two places.

My current hack/abuse is to use __new__ in a class that can 
contain the information:

   class foo(object):
     SPECIAL = 42
     MONKEY = 31415
     DEFAULT = SPECIAL
     def __new__(cls, arg1, arg2=DEFAULT):
       return int(do_stuff(arg1, arg2))

   i1 = foo("spatula")
   i2 = foo("tapioca", foo.MONKEY)

1) is this "icky" (a term of art ;-)
2) or is this reasonable
3) or is there a better way to do what I want?

Thanks,

-tkc