[Python-ideas] Where did we go wrong with negative stride?

[אלעזר]

2013/10/31 MRAB <python at mrabarnett.plus.com>:
> On 30/10/2013 23:00, Eric Snow wrote:
>>
>> On Wed, Oct 30, 2013 at 4:47 PM, Terry Reedy <tjreedy at udel.edu> wrote:
>>>
>>> I though of using a magic symbol, $, for that -- a[$-n]. But aside from
>>> the issue of using one of the 2 remaining unused ascii symbols for
>>> something that can already be done, it would not work in a slice call.
>>
>>
>> Is that like where you have 1 more shot on your camera and you don't
>> want to use it for fear that something more spectacular might show up
>> afterward?  (and hope that you didn't leave your lens cap on when you
>> finally take the picture!)  :-)
>>
> I don't think it's that bad; I count 3: "!", "$" and "?". :-)
>
Can't it be done by adding a __sub__ method to len?

a[:len-n]

Readable and short.