Wrapping around a list in Python.

shengjie.shengjie at live.com shengjie.shengjie at live.com
Mon Dec 16 06:26:49 CET 2013


On Monday, 16 December 2013 13:10:22 UTC+8, Gary Herron  wrote:
> On 12/15/2013 08:38 PM, shengjie.shengjie at live.com wrote:
> 
> > Hi guys, I am trying to create a fixed list which would allow my values to be wrapped around it.
> 
> > For example i have 10 values : 0,1,2,3,4,5,6,7,8,9
> 
> > I need to create a list which contains 4 numbers and when the number exceeds the list, it would overwrite the first value.
> 
> > [0,1,2,3]
> 
> > [4,1,2,3]
> 
> > [5,4,1,2]
> 
> >
> 
> > Thanks in advance and much help appreciated.
> 
> 
> 
> Is the output really three lists as you show.  Or is that one list whose 
> 
> contents you have shown three snapshots of?  Then what was the point of 
> 
> putting 4 in the first spot when you are just going to move it to the 
> 
> second spot?  And why stop at 4 and 5?  What about 7, 8, and 9?
> 
> 
> 
> Are you really shifting elements onto the beginning of the list and off 
> 
> the end of the list?  (That's easy to do, but is that what you want?)
> 
> 
> 
> If I follow your example a few elements further I get [9,8,7,6], just 
> 
> the last four elements of the original list in reverse order -- so there 
> 
> is no need fill a list and "wrap-around"  -- just grab the last four 
> 
> elements and reverse them.
> 
> 
> 
> Or have I misunderstood the problem completely?  (I think that's 
> 
> likely.)  I'm sure Python is general enough to do what you want, but 
> 
> you'll have to do a much better job telling is what you want.  While you 
> 
> are at it, tell us what you've already done, and how it fails to do 
> 
> whatever it is you want.
> 
> 
> 
> Gary Herron

The idea is to grab the last 4 elements of the array. However i have an array that contains a few hundred elements in it. And the values continues to .append over time. How would i be able to display the last 4 elements of the array under such a condition?



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