On Tue, 29 Oct 2013 08:53:08 +0000, Duncan Booth wrote: > Steven D'Aprano <st...@pearwood.info> wrote: > >> Does anyone here use slices (or range/xrange) with negative strides >> other than -1? >> >> E.g. sequence[2:15:-3] > > With any negative stride your example is just the empty sequence.
Gah, sorry about that, that's the suggested *new* syntax. Possibly my subconscious likes it better than my conscious :-) Try this instead: sequence[15:2:-3] >> If so, there is a discussion (long, long, looooooong discussion) on the >> python-ideas mailing list, debating whether or not to deprecate or >> change the behaviour of slicing with negative strides. So if you care >> about the current behaviour, now is the time to stand up and be >> counted. >> >> (Standing up *here* is fine, don't feel that you have to join yet >> another list.) >> > For those of us that don't really want to join another mailing list, > could you summarise what change is being proposed? * Negative strides should be deprecated and then removed. * Or just deprecated. * Or change the semantics of negative strides so that seq[2:15:-2] works as expected. * Or get rid of negative indexing. * Or add new syntax to control whether or not the end points are included. * Or ... It's Python-Ideas, otherwise known as Bike-Shed Central :-) I think the main idea which is likely (since Guido seems to be slightly leaning that way) is to deprecate negative strides, remove them in a release or three, and then re-introduce them in Python 4000 but with more intuitive semantics. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
