Yes it is; d[i:j] is equal to "give me the array from the d[i] to d[j - 1]", and if you omit i and j then the i and j are respectively assumed as 0 and len(d) - 1.
On Wed, Jun 2, 2010 at 8:01 PM, pmz <przemek.zaw...@gmail.com> wrote: > On 2 Cze, 19:56, geremy condra <debat...@gmail.com> wrote: >> On Wed, Jun 2, 2010 at 10:40 AM, pmz <przemek.zaw...@gmail.com> wrote: >> > Dear Group, >> >> > It's really rookie question, but I'm currently helping my wife in some >> > python-cases, where I'm non-python developer and some of syntax-diffs >> > make me a bit confused. >> >> > Could anyone give some light on line, as following: >> > "ds = d[:]" ### where 'd' is an array >> >> I'm guessing you mean that d is a list. The square >> braces with the colon is python's slicing notation, >> so if I say [1,2,3,4][0] I get a 1 back, and if I say >> [1,2,3,4][1:4] I get [2,3,4]. Python also allows a >> shorthand in slicing, which is that if the first index >> is not provided, then it assumes 0, and that if the >> second index is not provided, it assumes the end >> of the list. Thus, [1,2,3,4][:2] would give me [1,2] >> and [1,2,3,4][2:] would give me [3, 4]. Here, neither >> has been provided, so the slice simply takes the >> items in the list from beginning to end and returns >> them- [1,2,3,4][:] gives [1,2,3,4]. >> >> The reason someone would want to do this is >> because lists are mutable data structures. If you >> fire up your terminal you can try the following >> example: >> >> >>> a = [1,2,3,4] >> >>> b = a >> >>> c = [:] >> >>> b[0] = 5 >> >>> b >> [5,2,3,4] >> >>> # here's the issue >> >>> a >> [5,2,3,4] >> >>> # and the resolution >> >>> c >> >> [1,2,3,4] >> >> Hope this helps. >> >> Geremy Condra > > Thank you for such fast answer! I quite catch, but: > As I see, the d[:] is equal to sentence "get the d array from the > first to the last element"? :) > > P. > -- > http://mail.python.org/mailman/listinfo/python-list > -- Matteo Landi http://www.matteolandi.net/ -- http://mail.python.org/mailman/listinfo/python-list
