[Python-ideas] Specifying constants for functions

[Sven R. Kunze]

I totally agree here.

On 27.10.2015 19:18, Guido van Rossum wrote:
> IIRC it's an old micro-optimization; this was a common idiom at Zope. 
> But I think it's way overused -- people believe it works so they do it 
> all the time, even for code that's not performance sensitive, just 
> because it's become a habit. (Like "register" in C in the '80s.)
>
> On Tue, Oct 27, 2015 at 10:55 AM, Yury Selivanov 
> <yselivanov.ml at gmail.com <mailto:yselivanov.ml at gmail.com>> wrote:
>
>     Serhiy,
>
>     On 2015-10-27 1:45 PM, Serhiy Storchaka wrote:
>
>         There is known trick to optimize a function:
>
>             def foo(x, y=0, len=len, pack=struct.pack, maxsize=1<<BPF):
>                 ...
>
>         It has a side effect: change function's signature. Would be
>         nice to have a way to set function's local variables at
>         creation time without affecting a signature.
>
>
>     I see this a lot in all kinds of code.  In my experience it
>     doesn't actually speed things up in a measurable way.
>
>     Is the below code really much slower?
>
>         def foo(x, y=0):
>             pack=struct.pack
>             maxsize=1<<BPF
>             #CODE
>
>     If the #CODE is a tight long-running loop - then no, because the
>     loop will probably run much longer than an extra attribute lookup
>     + one extra bit shift on each "foo()" call.  And if there is no
>     tight loop - then you won't probably notice those optimizations
>     anyways.
>
>     I think that adding a "const" statement deserves some discussion,
>     but not from the standpoint of micro-optimizations.
>
>     Thanks,
>     Yury
>
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>
>
>
> -- 
> --Guido van Rossum (python.org/~guido <http://python.org/%7Eguido>)
>
>
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