Re: [Python-Dev] Python-Dev Digest, Vol 112, Issue 23

[Peter Harris]

Chris Withers wrote: 

On 14/11/2012 09:58, Merlijn van Deen wrote:
> On 14 November 2012 10:12, Chris Withers <ch...@simplistix.co.uk> wrote:
>> ...which made me a little sad
>
> Why did it make you sad? dict() takes 0.2?s, {} takes 0.04?s. In other
> words: you can run dict() _five million_ times per second, and {}
> twenty-five million times per second. That is 'a lot' and 'a lot'. It
> also means you are unlikely to notice the difference in real-world
> code. Just use the one you feel is clearer in the situation, and don't
> worry about micro-optimalization.

I'm inclined to agree, but it makes me sad for two reasons:

- it's something that people get hung up on, for better or worse. (if it
wasn't, Doug wouldn't have written his article)

- it can make a difference, for example setting up a dict with many keys
at the core of a type loop.

Without looking at implementation, they should logically perform the same...

Well, without looking at the implementation, you could form any opinion you

like about how they should perform. Still you could speculate that dict() will

require a builtins name lookup, and that the process of passing keyword arguments

might itself involve constructing a dictionary, so must inherently take at least

a little longer than compiling a {} literal.

Peter