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

MRAB python at mrabarnett.plus.com
Wed Feb 13 00:20:01 CET 2013

On 2013-02-12 21:44, Antoine Pitrou wrote:
> On Tue, 12 Feb 2013 16:40:38 -0500
> Ned Batchelder <ned at nedbatchelder.com> wrote:
>> But the only reason "".join() is a Python idiom in the first place is
>> because it was "the fast way" to do what everyone initially coded as "s
>> += ...".   Just because we all learned a long time ago that joining was
>> the fast way to build a string doesn't mean that "".join() is the clean
>> idiomatic way to do it.
> It's idiomatic because strings are immutable (by design, not because of
> an optimization detail) and therefore concatenation *has* to imply
> building a new string from scratch.
Tuples are much like immutable lists; sets were added, and then frozensets;
should we be adding mutable strings too (a bit like C#'s StringBuilder)?
(Just wondering...)

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