enhancing 'list'

samwyse samwyse at gmail.com
Mon Jan 18 12:22:59 CET 2010


On Jan 18, 1:56 am, Terry Reedy <tjre... at udel.edu> wrote:
> On 1/17/2010 5:37 PM, samwyse wrote:
>
>
>
>
>
> > Consider this a wish list.  I know I'm unlikely to get any of these in
> > time for for my birthday, but still I felt the need to toss it out and
> > see what happens.
>
> > Lately, I've slinging around a lot of lists, and there are some simple
> > things I'd like to do that just aren't there.
>
> > s.count(x[, cmp[, key]])
> > - return number of i‘s for which s[i] == x.  'cmp' specifies a custom
> > comparison function of two arguments, as in '.sort'.  'key' specifies
> > a custom key extraction function of one argument.
> > s.index(x[, i[, j[, cmp[, key]]]])
> > - return smallest k such that s[k] == x and i<= k<  j.  'cmp' and
> > 'key' are as above.
> > s.rindex(x[, i[, j[, cmp[, key]]]])
> > - return largest k such that s[k] == x and i<= k<  j.  'cmp' and
> > 'key' are as above.
>
> > There are two overlapping proposals here.  One is to add the .rindex
> > method, which strings already have.  The other is to extend the
> > optional arguments of .sort to all other methods that test for item
> > equality.
>
> > One last thing, the Python 2.6.2 spec says .count and .index only
> > apply to mutable sequence types.  I see no reason why they
> > (and .rindex) couldn't also apply to immutable sequences (tuples, in
> > particular).
>
> In 3.x, tuple does have those methods, even though the doc is not clear
> (unless fixed by now).

That's good to hear.  Perhaps I should have tried them directyly, but
my 3.1 docs still echo the 2.x docs, which only show them for
immutable sequences.



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