negative stride list slices

Reid Nichol rnichol_rrc at yahoo.com
Wed Sep 1 22:43:44 CEST 2004


Russell Blau wrote:
> "Reid Nichol" <rnichol_rrc at yahoo.com> wrote in message
> news:r7oZc.6653$MR2.32885 at news1.mts.net...
> 
>>David Abrahams wrote:
>>
>>>Can anyone explain the logic behind the behavior of list slicing with
>>>negative strides?  For example:
>>>
>>>  >>> print range(10)[:-3:-1]
>>>  [9,8]
>>>
>>>I found this result very surprising, and would just like to see the
>>>rules written down somewhere.
>>
> http://www.python.org/doc/current/tut/node5.html#SECTION005120000000000000000
> 
> You probably meant to reference the next section (that bookmark relates to
> strings, the next one is lists), but in either case none of the examples in
> the tutorial has yet been updated to deal with slices that include a
> "stride" as a third parameter.
> 
> 
This was the part that I was refering to:

  +---+---+---+---+---+
  | H | e | l | p | A |
  +---+---+---+---+---+
  0   1   2   3   4   5
-5  -4  -3  -2  -1


Does it not all work the same in practice?



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