[Python-3000] Making more effective use of slice objects in Py3k (original) (raw)

Jack Diederich jack at psynchronous.com
Thu Aug 31 06:43:54 CEST 2006

On Wed, Aug 30, 2006 at 08:56:03PM -0700, Bob Ippolito wrote:

On 8/30/06, Fredrik Lundh <fredrik at pythonware.com> wrote: > Fredrik Lundh wrote: > > > not necessarily, but there are lots of issues involved when doing > > high-performance XML stuff, and I'm not sure views would help quite as > > much as one might think. > > > > (writing and tuning cET was a great way to learn that not everything > > that you think you know about C performance applies to C code running > > inside the Python interpreter...) > > and also based on the cET (and NFS) experiences, it wouldn't surprise me > if a naive 32-bit text string implementation will, on average, slow things down > more than any string view implementation can speed things up again... > > (in other words, I'm convinced that we need a polymorphic string type. I'm not > so sure we need views, but if we have the former, we can use that mechanism to > support the latter)

+1 for polymorphic strings. This would give us the best of both worlds: compact representations for ASCII and Latin-1, full 32-bit text when needed, and the possibility to implement further optimizations when necessary. It could add a bit of complexity and/or a massive speed penalty (depending on how naive the implementation is) around character operations though. For implementation ideas, Apple's CoreFoundation has a mature implementation of polymorphic strings in C (which is the basis for their NSString type in Objective-C), and there's a cross-platform subset of it available as CF-Lite: http://developer.apple.com/opensource/cflite.html

Having watched Fredrik casually double the speed of many str and unicode operations in a week I'm easily +1 on whatever he says. Bob's support makes that a +2, he struck me as quite sane too.

That said can you guys expand on what polymorphic[1] means here in particular? Python wise I can only think of the str/unicode/buffer split. If the fraternity of strings doesn't include views (which I haven't needed either) what are you considering for the other kinds?

-Jack

[1] My ten pound Webster's says "An organism having more that one adult form, as the different castes in social ants" which is close enough to what I think the comp sci definition is.

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