insertion sorts...

[Maric Michaud]

Le Monday 30 June 2008 16:29:11 python_newbie, vous avez écrit :
> On 25 Haziran, 17:44, MRAB <goo... at mrabarnett.plus.com> wrote:
> > 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:
> > >    ....
> > >    new_list.append(x)
> > >
> > > 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.
> > >
> > > Sincerely,
> > > Albert
> >
> > 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
>
> Thanks again. I see that you use two different syntax for lists
> "mylist = new_list" and "mylist[:] = new_list" these are same i
> think ?

Not at all, try to figure out what happen with the following :

>>>[3]: l=[]

>>>[4]: g=[]

>>>[5]: l == g
...[5]: True

>>>[6]: l is g
...[6]: False

>>>[7]: l = [4]

>>>[8]: l is g
...[8]: False

>>>[9]: l == g
...[9]: False

>>>[10]: l = g

>>>[11]: l is g
...[11]: True

>>>[12]: l[:] = [4]

>>>[13]: l == g
...[13]: True

>>>[14]: l is g
...[14]: True

>>>[15]: g
...[15]: [4]



-- 
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Maric Michaud