enhancing 'list'

Steve Holden steve at holdenweb.com
Tue Jan 19 21:52:15 CET 2010

samwyse wrote:
> 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.

The tuple IS an immutable sequence.

Steve Holden           +1 571 484 6266   +1 800 494 3119
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