[Python-ideas] Enums

[Robert Kern]

On 7/25/11 4:39 PM, Michael Foord wrote:
>
>
> On 25 July 2011 21:47, Robert Kern <robert.kern at gmail.com
> <mailto:robert.kern at gmail.com>> wrote:
>
>     On 7/25/11 1:43 PM, Michael Foord wrote:
>
>         Some apis (for example those exported directly from C) can't work with
>         something
>         that isn't a real int.
>
>
>     I think almost all of those will usually accept an object that implements
>     __int__ and __index__, don't they? E.g.
>
>     [~]
>     |1> import os
>
>     [~]
>     |2> class A(object):
>     ..>     def __init__(self,x):
>     ..>         self.x = x
>     ..>     def __int__(self):
>     ..>         return self.x
>     ..>     def __index__(self):
>     ..>         return self.x
>     ..>
>
>     [~]
>     |10> os.open('foo', A(os.O_RDWR))
>     21
>
>
>     os.open() just uses PyArg_ParseTuple(), like most extension functions. I'm
>     sure you could write an extension function that would reject A() instances,
>     but it's more work, so most people don't.
>
>
> Providing __index__ may indeed be enough.

 From experiment with os.open() under 2.7 and 3.1, it is not enough, though 
perhaps either PyArg_ParseTuple() or PyInt_As*() should be modified to make it so.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco