Hi, On 20 August 2013 10:20, sikonai sikonai <tanjyu...@gmail.com> wrote:
> >>> list=[1,2,3,4,5,6,7,8,9] > >>> list[9:0:-2] > [9, 7, 5, 3] > >>> list[10:0:-2] > [9, 7, 5, 3] > > I want to know whether they have some difference. > For the specific list you show, the 2 expressions yield the same result. However this does not mean that this is true of any list. The reason the 2 expressions return the same result is because the starting index for the slice operation is effectively capped at 9, due to the list containing only 9 elements, so hence any value above 9 in the first slice parameter is essentially reset/capped to 9. For longer lists of course this is not true so the results are different. Play around with some longer/other examples to see this: Python 2.7.5 (default, May 15 2013, 22:43:36) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> l = [1,2,3,4,5,6,7,8,9,10,11] #note the extra elements as compared to your example >>> l[9:0] [] >>> l[9:0:-2] [10, 8, 6, 4, 2] >>> l[10:0:-2] [11, 9, 7, 5, 3] >>> l[12:0:-2] [11, 9, 7, 5, 3] >>> l[20:0:-2] [11, 9, 7, 5, 3] >>> Walter
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