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

Antoine Pitrou solipsis at pitrou.net
Thu Feb 14 08:38:58 CET 2013

On Thu, 14 Feb 2013 01:21:40 +0100 Victor Stinner <victor.stinner at gmail.com> wrote:

UnicodeWriter (using the "writer += str" API) is the fastest method in most cases, except for data = ['a'*104] * 102 (in this case, it's 8x slower!). I guess that the overhead comes for the overallocation which then require to shrink the buffer (shrinking may copy the whole string). The overallocation factor may be adapted depending on the size.

How about testing on Windows?

If computing the final length is cheap (eg. if it's always the same), it's always faster to use UnicodeWriter with a preallocated buffer.

That's not a particularly surprising discovery, is it? ;-)

Regards

Antoine.

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