[Python-Dev] Type of range object members

[Georg Brandl]

Neal Norwitz wrote:
> 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.

This might als be helpful when exceptions have to inherit from
BaseException in Py3k.

Georg