[Python-Dev] Usage of += on strings in loops in stdlib (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Tue Feb 12 22:06:42 CET 2013

Hi !

On Tue, 12 Feb 2013 23:03:04 +0200 Maciej Fijalkowski <fijall at gmail.com> wrote:

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)?

I agree that += should not be used as an optimization (on strings) in the stdlib code. The optimization is there so that uncareful code does not degenerate, but deliberately relying on it is a bit devilish. (optimisare diabolicum :-))

Regards

Antoine.

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