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

Dino Viehland dinov at microsoft.com
Fri Sep 2 14:57:06 EDT 2016

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 coextra 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

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