[Python-Dev] performance of {} versus dict()

[Oleg Broytman]

On Thu, Nov 15, 2012 at 12:18:38AM +1100, Chris Angelico <rosuav at gmail.com> wrote:
> On Wed, Nov 14, 2012 at 8:12 PM, Chris Withers <chris at simplistix.co.uk> wrote:
> > I suspect I'm not the only one who finds:
> >
> > a_dict = dict(
> >     x = 1,
> >     y = 2,
> >     z = 3,
> >     ...
> >     )
> >
> > ...easier to read than:
> >
> > a_dict = {
> >     'x':1,
> >     'y':2,
> >     'z':3,
> >     ...
> >     }
> >
> > What can we do to speed up the former case?
> 
> Perhaps an alternative question: What can be done to make the latter
> less unpalatable? I personally prefer dict literal syntax to a dict
> constructor call, but no doubt there are a number of people who feel
> as you do. In what way(s) do you find the literal syntax less
> readable, and can some simple (and backward-compatible) enhancements
> help that?
> 
> I've seen criticisms (though I don't recall where) of Python,
> comparing it to JavaScript/ECMAScript, that complain of the need to
> quote the keys. IMO this is a worthwhile downside, as it allows you to
> use variables as the keys, rather than requiring (effectively) literal
> strings. But it does make a dict literal that much more "noisy" than
> the constructor.

   On the other had it's more powerful. You can write {'class': 'foo'}
but cannot dict(class='bar'). {1: '1'} but not dict(1='1').

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            phd at phdru.name
           Programmers don't die, they just GOSUB without RETURN.