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

Chris Withers chris at simplistix.co.uk
Wed Nov 14 11:00:59 CET 2012

On 14/11/2012 09:58, Merlijn van Deen wrote:
> On 14 November 2012 10:12, Chris Withers <chris at simplistix.co.uk> wrote:
>> ...which made me a little sad
> Why did it make you sad? dict() takes 0.2µs, {} takes 0.04µs. 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...


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