On 09/13/2016 08:23 PM, Terry Wilson wrote:
On Tue, Sep 13, 2016 at 6:31 PM, Jay Pipes <jaypi...@gmail.com> wrote:
On 09/13/2016 01:40 PM, Terry Wilson wrote:

On Thu, Jun 11, 2015 at 8:33 AM, Sean Dague <s...@dague.net> wrote:

On 06/11/2015 09:02 AM, Jay Pipes wrote:

On 06/11/2015 01:16 AM, Robert Collins wrote:

But again - where in OpenStack does this matter the slightest?


Precisely. I can't think of a single case where we are iterating over
anywhere near the number of dictionary items that we would see any
impact whatsoever.


In neutron, the ovsdb native code iterates over fairly large
dictionaries since the underlying OVS library stores OVSDB tables
completely in memory as dicts. I just looked at the code I wrote and
it currently uses values() and I now want to switch it to
six.itervalues() :p.

Best,
-jay


+1.

This is a massive premature optimization which just makes all the code
gorpy for no real reason.


Premature optimization is about wasting a bunch of time trying to
optimize code before you know you need to, not about following the
accepted almost-always-faster/always-less-memory-using solution that
already exists. Memory-wise it's the difference between a constant
88-byte iterator and the storage for an additional list of tuples. And
if Raymond Hettinger, in a talk called "Transforming Code Into
Beautiful Idiomatic Python" specifically mentions that people should
always use iteritems
(https://www.youtube.com/watch?v=OSGv2VnC0go&feature=youtu.be&t=21m24s),
I tend to believe him. Sure, it'd be much better if Python 3 and
Python 2 both returned iterators for items(), values(), keys(), etc.,
but it doesn't. Wasting memory for purely aesthetic reasons (they're
even both the same number of lines) is just a bad idea, IMNSHO.


Is it wasted time to respond to a mailing list post from 18 months ago?

-jay

Ha! Absolutely it is. Someone posted a Neutron patch haphazardly
converting all of of the six.iteritems() calls to items() and it
struck a nerve. I searched for the thread in gmail not noticing the
date. My apologies! :)

Heh, no worries, I was mostly just being tongue-in-cheek :)

-jay

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