unicode() vs. s.decode()

[Thorsten Kampe]

* Steven D'Aprano (08 Aug 2009 03:29:43 GMT)
> On Fri, 07 Aug 2009 17:13:07 +0200, Thorsten Kampe wrote:
> > One guy claims he has times between 2.7 and 5.7 seconds when
> > benchmarking more or less randomly generated "one million different
> > lines". That *is* *exactly* nothing.
> 
> We agree that in the grand scheme of things, a difference of 2.7 seconds 
> versus 5.7 seconds is a trivial difference if your entire program takes 
> (say) 8 minutes to run. You won't even notice it.

Exactly.

> But why assume that the program takes 8 minutes to run? Perhaps it takes 
> 8 seconds to run, and 6 seconds of that is the decoding. Then halving 
> that reduces the total runtime from 8 seconds to 5, which is a noticeable 
> speed increase to the user, and significant if you then run that program 
> tens of thousands of times.

Exactly. That's why it doesn't make sense to benchmark decode()/unicode
() isolated - meaning out of the context of your actual program.

> By all means, reminding people that pre-mature optimization is a 
> waste of time, but it's possible to take that attitude too far to Planet 
> Bizarro. At the point that you start insisting, and emphasising, that a 
> three second time difference is "*exactly*" zero,

Exactly. Because it was not generated in a real world use case but by 
running a simple loop one millions times. Why one million times? Because 
by running it "only" one hundred thousand times the difference would 
have seen even less relevant.

> it seems to me that this is about you winning rather than you giving
> good advice.

I already gave good advice:
1. don't benchmark
2. don't benchmark until you have an actual performance issue
3. if you benchmark then the whole application and not single commands

It's really easy: Michael has working code. With that he can easily 
write two versions - one that uses decode() and one that uses unicode(). 
He can benchmark these with some real world input he often uses by 
running it a hundred or a thousand times (even a million if he likes). 
Then he can compare the results. I doubt that there will be any 
noticeable difference.

Thorsten