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