I'm very glad folk are working on Python3 ports. I'd like to call attention to one little wart in that process: I get the feeling that folk are applying a massive regex to find things like d.iteritems() and convert that to six.iteritems(d).
I'd very much prefer that such a regex approach move things to d.items(), which is much easier to read. Here's why. Firstly, very very very few of our dict iterations are going to be performance sensitive in the way that iteritems() matters. Secondly, no really - unless you're doing HUGE dicts, it doesn't matter. Thirdly. Really, it doesn't. At 1 million items the overhead is 54ms[1]. If we're doing inner loops on million item dictionaries anywhere in OpenStack today, we have a problem. We might want to in e.g. the scheduler... if it held in-memory state on a million hypervisors at once, because I don't really to to imagine it pulling a million rows from a DB on every action. But then, we'd be looking at a whole 54ms. I think we could survive, if we did that (which we don't). So - please, no six.iteritems(). Thanks, Rob [1] python2.7 -m timeit -s 'd=dict(enumerate(range(1000000)))' 'for i in d.items(): pass' 10 loops, best of 3: 76.6 msec per loop python2.7 -m timeit -s 'd=dict(enumerate(range(1000000)))' 'for i in d.iteritems(): pass' 100 loops, best of 3: 22.6 msec per loop python3.4 -m timeit -s 'd=dict(enumerate(range(1000000)))' 'for i in d.items(): pass' 10 loops, best of 3: 18.9 msec per loop pypy2.3 -m timeit -s 'd=dict(enumerate(range(1000000)))' 'for i in d.items(): pass' 10 loops, best of 3: 65.8 msec per loop # and out of interest, assuming that that hadn't triggered the JIT.... but it had. pypy -m timeit -n 1000 -s 'd=dict(enumerate(range(1000000)))' 'for i in d.items(): pass' 1000 loops, best of 3: 64.3 msec per loop -- Robert Collins <rbtcoll...@hp.com> Distinguished Technologist HP Converged Cloud __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
