[Python-Dev] Update on PEP 523 and adding a co_extra field to code objects

[Dino Viehland]

So it looks like both list and tuple are about within 5% of using co_extra directly.  Using a tuple instead of a list is about a wash except for make_v2 where list is 1.4x slower for some reason (which I didn't dig into).

I would say that using a tuple and copying the tuple on updates makes sense as we don't expect these to change very often and we don't expect collisions to happen very often.

> -----Original Message-----
> From: Python-Dev [mailto:python-dev-
> bounces+dinov=microsoft.com at python.org] On Behalf Of Chris Angelico
> Sent: Tuesday, August 30, 2016 2:11 PM
> To: python-dev <python-dev at python.org>
> Subject: Re: [Python-Dev] Update on PEP 523 and adding a co_extra field to
> code objects
> 
> On Wed, Aug 31, 2016 at 4:55 AM, Serhiy Storchaka <storchaka at gmail.com>
> wrote:
> > On 30.08.16 21:20, Antoine Pitrou wrote:
> >>
> >> On Tue, 30 Aug 2016 18:12:01 +0000
> >> Brett Cannon <brett at python.org> wrote:
> >>>>
> >>>> Why not make it always a list?  List objects are reasonably cheap
> >>>> in memory and access time... (unlike dicts)
> >>>
> >>>
> >>> Because I would prefer to avoid any form of unnecessary performance
> >>> overhead for the common case.
> >>
> >>
> >> But the performance overhead of iterating over a 1-element list is
> >> small enough (it's just an array access after a pointer dereference)
> >> that it may not be larger than the overhead of the multiple tests and
> >> conditional branches your example shows.
> >
> >
> > Iterating over a tuple is even faster. It needs one pointer
> > dereference less.
> >
> > And for memory efficiency we can use just a raw array of pointers.
> 
> Didn't all this kind of thing come up when function annotations were
> discussed? Insane schemes like dictionaries with UUID keys and so on.
> The decision then was YAGNI. The decision now, IMO, should be the same.
> Keep things simple.
> 
> ChrisA
> _______________________________________________
> Python-Dev mailing list
> Python-Dev at python.org
> https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fmail.pyt
> hon.org%2fmailman%2flistinfo%2fpython-
> dev&data=01%7c01%7cdinov%40microsoft.com%7c9d750b06b2134a2145c70
> 8d3d11a4ab0%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=szub1gs
> DW2rdns3IQGV68J3tCqWiNcjqG77xYIfoORc%3d
> Unsubscribe:
> https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fmail.pyt
> hon.org%2fmailman%2foptions%2fpython-
> dev%2fdinov%2540microsoft.com&data=01%7c01%7cdinov%40microsoft.co
> m%7c9d750b06b2134a2145c708d3d11a4ab0%7c72f988bf86f141af91ab2d7c
> d011db47%7c1&sdata=TEzMSyJLmAe2BVZGPugXAh6bga2xN1WQw3bR0z0b
> %2fLg%3d