On Tue, Feb 12, 2013 at 1:03 PM, Maciej Fijalkowski email@example.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.
Just to confirm Jython does not have optimizations for += String and will do much better with the idiomatic "".join().