StringChain -- a data structure for managing large sequences of chunks of bytes

Steven D'Aprano steve at
Sat Mar 13 04:06:52 CET 2010

On Fri, 12 Mar 2010 13:40:23 +0000, MRAB wrote:

>> To be taken seriously, I think you need to compare stringchain to the
>> list idiom. If your benchmarks favourably compare to that, then it
>> might be worthwhile.
> IIRC, someone did some work on making concatenation faster by delaying
> it until a certain threshold had been reached (in the string class
> implementation).

I believe you're talking about this patch:

It's never been formally rejected, but the chances of it being accepted 
are pretty low.

However, in Python 2.4 another optimization was added that makes string 
concatenation of the form:

a = a + b
a += b

much faster. This is implementation specific (Jython and IronPython don't 
have it, and almost certainly won't) and it doesn't work for (e.g.):

a = b + a

See here:


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