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@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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