[Tutor] help with slice

bob gailer bgailer at alum.rpi.edu
Wed Mar 5 01:20:31 CET 2008

bob gailer wrote:
> washakie wrote:
>> Could someone please explain 'slices' also for dictionaries?
>> basically, I'd like to know how you would call every 3rd element in a list
>> of lists... 
Call? Do you mean that these elements are callable objects (e.g. 
functions) which you want to "call", or are you just trying to get a 
list of the elements? My answer below addresses the 2nd meaning.

>> My logic says: ThirdElems=List[:][2]
>> Which to me reads, for every item in List (which are lists), return the
>> third item.
> That is wishful reading. No basis in reality. List[:] gives you a 
> shallow copy of List. [2] then refers to the 3rd element of that copy.
> Try: [sublist[2] for sublist in List]

Bob Gailer
919-636-4239 Chapel Hill, NC

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