[Python-3000] long/int unification (original) (raw)

Travis Oliphant oliphant at ee.byu.edu
Wed Sep 6 01:25:06 CEST 2006

Guido van Rossum wrote:

On 9/5/06, Travis Oliphant <oliphant.travis at ieee.org> wrote:

What impact is this long/int unification going to have on C-based sub-types of the old int-type? Will you be able to sub-class the integer-type in C without carrying around all the extra backage of the Python long? This seems unlikely given that the PyInt type will go away (though the PyInt API methods may well continue to exist). You can subclass the PyLong type just as easily. What baggage are you thinking of?

Just the extra stuff in the C-structure needed to handle the arbitrary-length integer.

If you're thinking of the current special-casing for e.g. list[int] in ceval.c, that code will likely disappear (although something equivalent will eventually be added).

Yes, that's what I'm thinking of. It would be nice if the "something equivalent" could be extended to other objects. I suppose the discussion can be held off until then.

But now that we have index, of course, there's less reason to subclass PyInt in the first place -- you can write your own 32-bit integer without inheriting from PyInt or PyLong, and it should be usable perfectly whenever an integer is expected. Id rather make sure this property is provided without compromise than attempting to keep random older optimizations alive for nostalgia's sake.

Of course, I agree entirely, so I doubt it will matter at all (except in optimizations). There is probably going to be an increasing need to tell whether or not something can handle one of these interfaces. I know this was already discussed on this list, but was a decision reached about how to tell if something exposes a specific interface? (I think the relevant discussion took place under the name "callable").

I see a lot of

isinstance(obj, int)

in scientific Python code where testing for index would be more appropriate.

Thanks for easing my mind.

-Travis

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