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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Mon, 29 Oct 2012 17:01:29 -0600
Subject: Re: Negative array indicies and slice()
To: Python <python-list@python.org>
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On Mon, Oct 29, 2012 at 9:20 AM, Andrew Robinson
<andrew3@r3dsolutions.com> wrote:
> FYI: I was asking for a reason why Python's present implementation is
> desirable...
>
> I wonder, for example:
>
> Given an arbitrary list:
> a=[1,2,3,4,5,6,7,8,9,10,11,12]
>
> Why would someone *want* to do:
> a[-7,10]
> Instead of saying
> a[5:10] or a[-7:-2] ?

A quick search of local code turns up examples like this:

if name.startswith('{') and name.endswith('}'):
    name = name[1:-1]

If slices worked like ranges, then the result of that would be empty,
which is obviously not desirable.

I don't know of a reason why one might need to use a negative start
with a positive stop, though.