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[Python-Dev] Usage of += on strings in loops in stdlib

Nick Coghlan ncoghlan at gmail.com
Wed Feb 13 00:39:23 CET 2013 
On 13 Feb 2013 07:08, "Maciej Fijalkowski" <fijall at gmail.com> wrote:
>
> Hi
>
> We recently encountered a performance issue in stdlib for pypy. It
> turned out that someone commited a performance "fix" that uses += for
> strings instead of "".join() that was there before.
>
> Now this hurts pypy (we can mitigate it to some degree though) and
> possible Jython and IronPython too.
>
> How people feel about generally not having += on long strings in
> stdlib (since the refcount = 1 thing is a hack)?
>
> What about other performance improvements in stdlib that are
> problematic for pypy or others?
>
> Personally I would like cleaner code in stdlib vs speeding up CPython.

For the specific case of "Don't rely on the fragile refcounting hack in
CPython's string concatenation" I strongly agree. However, as a general
principle, I can't agree until speed.python.org is a going concern and we
can get a reasonable overview of any resulting performance implications.

Regards,
Nick.

> Typically that also helps pypy so I'm not unbiased.
>
> Cheers,
> fijal
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