On Feb 14, 4:47 pm, Steven D'Aprano <st...@pearwood.info> wrote: > > Sammo <sammo2828 <at> gmail.com> writes: > >> String concatenation has been optimized since 2.3, so using += should > >> be fairly fast. > > > This is implementation dependent and shouldn't be relied upon. > > It's also a fairly simple optimization and really only applies to direct > object access, not items or attributes. > > >> Why is the second test so much slower? > > > Probably several reasons: > > > 1. Function call overhead is quite large compared to these simple > > operations. 2. You are resolving attribute names. > > 3. Because the optimization isn't applied in this case.
Thanks Steven -- that's the answer I was looking for. The += string concatenation optimization only applies to local variables. In my case, I incorrectly assumed it applied to attributes. Can you point me to any references regarding the limitations of the optimization? I guess it's another Python idiom that's documented somewhere ... -- http://mail.python.org/mailman/listinfo/python-list
