[Python-3000] Automatically invoking str() in str.join()

[Crutcher Dunnavant]

On 4/27/06, Alex Martelli <aleaxit at gmail.com> wrote:
> On 4/27/06, Barry Warsaw <barry at python.org> wrote:
> > On Thu, 2006-04-27 at 10:08 -0700, Aahz wrote:
> >
> > > While I hate the way it looks, I never have gotten mixed up about the
> > > order of arguments since switching to ''.join(l).
> >
> > Which is why
> >
> > EMPTYSTRING = ''
> >
> > ...
> >
> > EMPTYSTRING.join(seq)
> >
> > looks much better.  But hey, yeah, a join() builtin would be fine if it
> > took the string arg first, so that
> >
> > ''.join(seq) == join('', seq)
>
> I think I would prefer a signature of:
>     join(seq, joiner='')

Just because I have to, why not consider a join operator?

Lets look at a simple case, the one matching SEP.join(SEQ), and try
using | as the join op (though others, such as <>, ~, @, ::, |>, etc.
are available):

SEQ | SEP := SEQ[1] + SEP + SEQ[2] + SEP + ...

Perhaps though, we'd like a family similar to OP=, so we'd have OP|,
and we could say:

SEQ +| SEP := SEQ[1] + SEP + SEQ[2] + SEP + ...

Though this is a bit unwieldy. Perhaps it is time to support something
like the Infix class from the cookbook:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/384122

This would let us decorate a join builtin with the infix decorator,
and then say:

SEQ |join| SEP, or, depending upon the join arg order, SEP |join| SEQ

> Rationale: an emptystring joiner is the most frequent cases, but
> several others (space, newline, space-comma, ...) occur often enough
> to be worth allowing the joiner to be optionally specified.
>
> The ability to omit the joiner in most cases works particularly well
> with genexps, e.g.
>
> join(str(x) for x in whatever)
>
> ve
>
> join('', (str(x) for x in whatever))
>
>
> Alex
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--
Crutcher Dunnavant <crutcher at gmail.com>
littlelanguages.com
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