Please don't top post. :)
tbour...@doc.ic.ac.uk wrote:
On Thu, Nov 19, 2009 at 3:00 AM, Rami Chowdhury
<rami.chowdh...@gmail.com <mailto:rami.chowdh...@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.
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
So "shallow copy" == "new label created for existing object".
So is your desired behavior to write back to the original list if your
sub-list is modified? In other words, you are creating a window onto an
existing list? If not, what would happen when a sublist element was
modified (or deleted, or appended, or ...)?
~Ethan~
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