non-copy slices

[tbourden at doc.ic.ac.uk]

No I'm well aware that there is no deep copy of the objects and the lists
only keep references to the objects and in essence they have the same
objects in there. But this doesn't mean they are the same list.
Modifications to slices are not written back to the original list.

x = range(5)
y = x[1:3]
y[0] = 13
x[1] == y[0]  --> False

Of course if I modify the object in the slice then the original list will
see the change, but this is not what I was saying. Second and more
importantly it's the performance penalty from allocating a large number of
lists produced from the slices and the copy of the references. islice does
not have this penalty, it should only instantiate a small object that
iterates on the original list.

Themis


On Thu, Nov 19, 2009 at 3:00 AM, Rami Chowdhury <rami.chowdhury at gmail.com>wrote:

>
> I'm not sure you're understanding the point others have been making. A
> list item is merely another reference to an existing object -- it
> doesn't copy the object in any way.
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-list/attachments/20091119/208e3d26/attachment-0001.html>