[Python-3000] String formating operations in python 3k

[Crutcher Dunnavant]

On 4/2/06, Georg Brandl <g.brandl at gmx.net> wrote:
> Crutcher Dunnavant wrote:
> > Python currently supports  'S % X', where S is a strinng, and X is one of:
> > * a sequence
> > * a map
> > * treated as (X,)
> >
> > But I have some questions about this for python 3000.
> >
> > 1. Shouldn't there be a format method, like S.format(), or S.fmt()?
>
> Possible, but why? "%" works quite fine. "Abusing" the modulus operator
> is okay in this context since the symbol gives a nonoverseeable clue to
> what the construct is doing.

Why? Because:
1 It is trivially cheap, format() would be the same function as __rmod__
2 It adds consistency with lower(), strip(), and other methods which
produce new strings.
3 I am not arguing _against_ syntactic support, I am arguing _for_ a method;
   we can keep the syntactic support.

>
> > 2. What about using __call__ instead of / in addition to __rmod__?
> > * "time: %s"(time.ctime()) == "time: %s" % time.ctime()
> > * "%(a)s %(b)s"(a=1, b=2) == "%(a)s %(b)s" % {'a'=1, 'b'=2}
>
> Damn ugly. How would you explain to a newbie that you can _call_ a string?
> And that _calling_ a string does a formatting operation?
> For me, string formatting with "%" is fine as it is.

This is a non-argument. I'd do it the same way that we currently explain that
you can _modulo_ or _multiply_ a string.

The basic argument goes something like this:
While addition and multiplication are binary operations, string
formatting usually has more elements involved, and as such, treating
it as a binary operation is a bit strange. Especially when keyword
formatting is involved. It so happens that python has a well developed
syntax for exactly this sort of relationship, and it is the _call_
syntax. So this reduces the complexity of the language for the
learner.


>
> BTW, has anyone seen string.Template being used somewhere?
>
> Georg
>
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Crutcher Dunnavant <crutcher at gmail.com>
littlelanguages.com
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