[Python-Dev] Type of range object members (original) (raw)

Neal Norwitz nnorwitz at gmail.com
Wed Aug 16 08:46:26 CEST 2006

On 8/15/06, "Martin v. Löwis" <martin at v.loewis.de> wrote:

That penalty is already paid today. Much code dealing with ints has a type test whether it's an int or a long. If int and long become subtypes of each other or of some abstract type, performance will decrease even more because a subtype test is quite expensive if the object is neither int nor long (it has to traverse the entire base type hierarchy to find out its not inherited from int).

I was playing around with a little patch to avoid that penalty. It doesn't take any additional memory, just a handful of bits we aren't using. :-)

For the more common builtin types, it stores whether it's a subclass in tp_flags, so there's no function call necessary and it's a constant time operation. It was faster when doing simple stuff. Haven't thought much whether this is really worthwhile or not.

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