On Sat, Jun 29, 2019 at 9:02 AM Andrew Barnert <abarn...@yahoo.com> wrote:
>
> On Jun 28, 2019, at 12:09, Chris Angelico <ros...@gmail.com> wrote:
> >
> > 1) For all the different types of object that can be read (integer,
> > string, JSON blob, etc), have a function that will read one, stop when
> > it's done, and report both the parsed object and the point where it
> > stopped parsing.
>
> For a string, what does it mean to “read one”? Does it just munch everything,
> or until the end of the line (whether \n or universal newlines), or until
> white space, or just one character? Whichever one you decide is right is
> probably trivial to implement (value, _, rest = arg.partition('\n')), but
> unless the goal is “exactly what C scanf does” (in which case I’m not sure we
> need a whole protocol-and-wrapper thing), there doesn’t seem to be a TOOWTDI
> answer here.
>
The %s marker would accept everything up to the next literal text. So
if you say "%s@%s", it would read up to the at sign. The second part
of the proposal would be doing that, though; the "%s" handler would
simply accept everything and return it.
> Meanwhile, the json module can already do this with the raw decode method
> (although you to have to construct a decoder instance, as it doesn’t have a
> convenience wrapper like loads), and so can lots of other things (even stuff
> like struct.unpack_from), but they mostly have a wide range of inconsistent
> APIs. Maybe just having a consistent “val, rest = parse_one(source_str,
> type)” function that calls a dunder protocol type.__parse_one__(source_str)
> or accesses a registry that each module can add to (and users can customize),
> or …?
>
Yes, that's what I mentioned as being possible to hack around with
JSON parsing, but it's not exactly an API, and it's something that
could be done way better for other protocols too.
ChrisA
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