On 2 Cze, 20:07, Matteo Landi <landima...@gmail.com> wrote: > Anyway I suggest you to use a syntax like: > > >>>b = list(a) > > in order to copy a list, it should be better than slicing. > > > > > > On Wed, Jun 2, 2010 at 7:56 PM, 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 > > -- > >http://mail.python.org/mailman/listinfo/python-list > > -- > Matteo Landihttp://www.matteolandi.net/
In fact, that ain't my syntax, I'd rather use C++ for that project, because that's my world is not Python, but thank you anyway for help - I see that Python also has many fans and friends online :) I'll try help her using your explanations. THANK you again and all the best, Przemek M. Zawada -- http://mail.python.org/mailman/listinfo/python-list
