[Python-Dev] PEP 0008 confusion - here it is, but don't use it?
python at rcn.com
Fri Aug 6 09:32:21 CEST 2004
> I'm a bit confused. Why bother to speed up s+=t if we aren't supposed
> use it?
In fact, it is does occur all over the place (esp. in newbie code) so it
ought to run as fast as possible or least not be a total disaster.
OTOH, library code gets run on various implementations of Python and it
would be a mistake to change any library code from ''.join() and have it
start performing badly on other implementations. That was essentially
the only argument against the patch which is otherwise a pure win.
On a side note, the += optimization only works if there is space
(fragmentationwise, not total memory) to resize a string in-place.
While this is usually true, ''.join() always runs in linear time. Also,
''.join() doesn't run through the eval-loop. IOW, notwithstanding
cross-implementation performance, ''.join() is usually a better choice
in performance sensitive code.
The goal of the patch is not to change coding styles. Rather, the goal
is to have it hurt less when you coded += anyways.
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