non-copy slices

[tbourden at doc.ic.ac.uk]

Hi,

sth == something :) sorry for the abbreviation. I'm talking about the
shallow copy, still it's a copy. Unnecessary in my case and the worst part
in my scenario is the creation (allocation) and deletion of a very large
number of lists of moderate size (a few hundred objects) generated due to
slices, while I only need to have a restricted view on the original list.
The islice class partially solves the problem as I mentioned in the previous
emails.

Cheers,
Themis


On Wed, Nov 18, 2009 at 3:44 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

> tbourden at doc.ic.ac.uk wrote:
> > Hi,
> >
> > I was looking for a facility similar to slices in python library that
> > would avoid the implicit creation of a new list and copy of elements
> > that is the default behaviour. Instead I'd rather have a lazy iteratable
> > object on the original sequence. Well, in the end I wrote it myself but
> > I was wondering if I missed sth in the library. If I didn't is there a
> > particular reason there isn't sth like that? I find it hard to believe
> > that all slice needs have strictly copy semantics.
> >
> > Cheers,
> > Themis
>
> Two questions:  1) What is "sth"?  and 2), What copy?
>
> Python 2.5.4 (r254:67916, Dec 23 2008, 15:10:54) [MSC v.1310 32 bit
> (Intel)]
> In [1]: class dummy(object):
>    ...:     pass
>    ...:
>
> In [2]: a = dummy()
> In [3]: b = dummy()
> In [4]: c = dummy()
> In [5]: d = dummy()
> In [6]: e = dummy()
> In [7]: list1 = [a, b, c, d, e]
> In [8]: list1
> Out[8]:
> [<__main__.dummy object at 0x0130C510>,
>  <__main__.dummy object at 0x013F1A50>,
>  <__main__.dummy object at 0x00A854F0>,
>  <__main__.dummy object at 0x00A7EF50>,
>  <__main__.dummy object at 0x00A7E650>]
>
> In [9]: list2 = list1[1:3]
> In [10]: list2
> Out[10]:
> [<__main__.dummy object at 0x013F1A50>,
>  <__main__.dummy object at 0x00A854F0>]
>
> In [11]: list2[0] is list1[1]
> Out[11]: *True*
> In [12]: list2[1] is list1[2]
> Out[12]: *True*
>
> No copying of items going on here.  What do you get?
>
> ~Ethan~
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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