[Python-ideas] strings as iterables - from str.startswith taking any iterator instead of just tuple

[Masklinn]

On 2014-01-04, at 23:59 , Steven D'Aprano <steve at pearwood.info> wrote:
> On Sat, Jan 04, 2014 at 11:22:16AM +0100, spir wrote:
>> On 01/03/2014 07:11 PM, Bruce Leban wrote:
>>> As to the idea of making strings not iterable, that would break my code. I
>>> write a lot of code to manipulate words (to create puzzles) and iterating
>>> over strings is fundamental. In fact, I'd like to have strings as results
>>> of iteration operations on strings:
>>> 
>>>>>>>>> sorted('string')
>>> 'ginrst'
>>>>>>>>> list(itertools.permutations('bar'))
>>> ['bar', 'bra', 'abr', 'arb', 'rba', 'rab']
> 
> That would be nice to have.

More generally, it would be nice if a sequence type could specify how to
derive a new instance of itself (from an iterable for instance).
Constructors don't necessarily work (e.g. str's constructor). Clojure
has such a concept through the IPersistentCollection protocol:
empty(coll) creates a new (empty) instance of coll (clojure's
collections being immutable, it makes sense to create an empty
collection then add stuff into it via into() or conj())