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

[Antoine Pitrou]

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.

Regards

Antoine.