String performance regression from python 3.2 to 3.3

Terry Reedy tjreedy at
Fri Mar 15 00:14:32 CET 2013

On 3/14/2013 6:48 AM, rusi wrote:
> On Mar 14, 11:47 am, Chris Angelico <ros... at> wrote:
> <snipped>
>> I expect that Python 3.2 will behave comparably to the 2.6 stats, but
>> I don't have 3.2s handy - can someone confirm please?
> I have 3.2 but not 3.3. Can run it later today if no one does.
> But better if someone with both on the same machine do the comparison.

The python devs use the microbenchmarks in 
Tools/stringbench/, which covers all string operations, as 
the basis for improving particular string functions. Overall, Unicode is 
nearly as fast as bytes and 3.3 as fast as 3.2. Find/replace is the 
notable exception in stringbench, so it is an anomaly. Other things are 
faster in 3.3.  In selecting the new implementation, the devs also 
considered space and speed gains that do not show up in microbenchmarks.

Terry Jan Reedy

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