google at mrabarnett.plus.com
Wed Jun 25 16:44:50 CEST 2008
On Jun 25, 11:37 am, "A.T.Hofkamp" <h... at se-162.se.wtb.tue.nl> wrote:
> On 2008-06-25, python_newbie <serbule... at gmail.com> wrote:
> > On 24 Haziran, 04:33, Terry Reedy <tjre... at udel.edu> wrote:
> > Thanks for all answers. At the end i ve only one point. If a decide to
> > copy list to iterate when will i have to do this ? Before the
> > iteration ? And then iterate through one list and change value of the
> > other ?
> Before starting the iteration would be a good point....
> I usually do in such cases:
> for x in mylist[:]:
> making a copy just before the for loop starts.
> Lately, I have started avoiding in-place modification of lists. Instead, I
> construct a new list from scratch inside the for-loop, and replace the old list
> with the newly constructed list afterwards like:
> new_list = 
> for x in mylist:
> mylist = new_list
> by appending a different value than the original or by not appending, you can
> influence the contents of the new list.
> I find this solution nicer than in-place modification of an existing list.
And if you were originally doing in-place modification because there
were also other references to the list then you could just do:
mylist[:] = new_list
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