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Re: Storing instances using jsonpickle

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On Thu, Sep 4, 2014 at 9:39 AM, MRAB <python@mrabarnett.plus.com> wrote:
> I occasionally think about a superset of JSON, called, say, "pyson" ...
> ah, name already taken! :-(

While I'm somewhat sympathetic to the concept, there are some parts of
your description that I disagree with. Am I misreading something? Are
there typos in the description and I'm making something out of
nothing?

> It would add tuples, delimited by (...), which are not used otherwise (no
> expressions):
>
>     () => ()
>     (0, ) => (0)

This seems odd. Part of JSON's convenience is that it's a subset of
JavaScript syntax, so you can just plop a block of JSON into a REPL
and it'll decode correctly. With PyON (or whatever you call it), it'd
be nice to have the same correspondence; for a start, I would strongly
encourage the "trailing comma is permitted" rule (so [1,2,3,] is
equivalent to [1,2,3]), and then I'd have the default encoding for a
single-element tuple include that trailing comma. If (0) is a
one-element tuple, you end up with a subtle difference between a PyON
decode and the Python interpreter, which is likely to cause problems.
It might even be worth actually mandating (not just encouraging) that
one-element tuples have the trailing comma, just to prevent that.

> The key of a dict could also be int, float, or tuple.

Yes! Yes! DEFINITELY do this!! Ahem. Calm down a little, it's not that
outlandish an idea...

> It could support other classes, and could handle named arguments.
>
> For example, sets:
>
> To encode {0, 1, 2):

Do you mean {0, 1, 2} here? I'm hoping you aren't advocating a syntax
that mismatches bracket types. That's only going to cause confusion.

>     Look in encoder dict for encoder function with class's name ('set') and
> call it, passing object.
>
>     Encoder returns positional and keyword arguments: [0, 1, 2] and {}.
>
>     Output name, followed by encoded arguments in parentheses.
>
>     Encoder for set:
>
>     def encode_set(obj):
>         return list(obj), {}
>
> To decode 'set(0, 1, 2)':
>
>     Parse name: 'set'.
>
>     Parse contents of parentheses: [0, 1, 2] and {}.
>
>     Look in decoder dict for decoder function with given name ('set') and
> call it, passing arguments.
>
>     Result would be {0, 1, 2}.
>
>     Decoder for set:
>
>     def decode_set(*args):
>         return set(args)
>
> pyson.dumps({0, 1, 2}, decoders={'set': decode_set}) would return 'set(0, 1,
> 2)'.
>
> pyson.loads('set(0, 1, 2)', encoders={'set': encode_set}) would return {0,
> 1, 2}.

This seems very much overengineered. Keep it much more simple; adding
set notation is well and good, but keyword arguments aren't necessary
there, and I'm not seeing a tremendous use-case for them.

It's a pity Python has the collision of sets and dicts both using
braces. Pike went for two-character delimiters, which might be better
suited here; round brackets aren't used in JSON anywhere, so you can
afford to steal them:

{'this':'is', 'a':'dict'}
({'this','is','a','set'})

Empty sets would be an issue, though, as they'll be different in
Python and this format. But everything else would work fine. You have
a two-character delimiter in PyON, and superfluous parentheses around
set notation in Python.

(Sadly, this doesn't make it Pike-compatible, as Pike uses (<x,y,z>)
for sets. But it wouldn't have been anyway.)

ChrisA

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Thread

Storing instances using jsonpickle Josh English <Joshua.R.English@gmail.com> - 2014-09-03 13:32 -0700
  Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-03 16:52 -0400
    Re: Storing instances using jsonpickle Josh English <Joshua.R.English@gmail.com> - 2014-09-03 15:30 -0700
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-04 00:39 +0100
        Re: Storing instances using jsonpickle Denis McMahon <denismfmcmahon@gmail.com> - 2014-09-04 01:11 +0000
      Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-03 22:18 -0400
        Re: Storing instances using jsonpickle Sam Raker <sam.raker@gmail.com> - 2014-09-03 21:52 -0700
        Re: Storing instances using jsonpickle Josh English <Joshua.R.English@gmail.com> - 2014-09-15 12:30 -0700
      Re: Storing instances using jsonpickle Chris Angelico <rosuav@gmail.com> - 2014-09-04 15:17 +1000
        Re: Storing instances using jsonpickle Dan Sommers <dan@tombstonezero.net> - 2014-09-05 04:38 +0000
          Re: Storing instances using jsonpickle Chris Angelico <rosuav@gmail.com> - 2014-09-05 15:08 +1000
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-04 12:07 +0100
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-05 18:04 +0100
        Re: Storing instances using jsonpickle Marko Rauhamaa <marko@pacujo.net> - 2014-09-05 20:16 +0300
          Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-05 13:30 -0400
            Re: Storing instances using jsonpickle Marko Rauhamaa <marko@pacujo.net> - 2014-09-05 21:04 +0300
              Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-05 16:50 -0400
                Re: Storing instances using jsonpickle Marko Rauhamaa <marko@pacujo.net> - 2014-09-05 23:57 +0300
          Re: Storing instances using jsonpickle Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2014-09-06 00:18 +0200
      Re: Storing instances using jsonpickle Chris Angelico <rosuav@gmail.com> - 2014-09-06 10:20 +1000
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-06 17:32 +0100
      Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-06 12:56 -0400
      Re: Storing instances using jsonpickle Terry Reedy <tjreedy@udel.edu> - 2014-09-06 14:27 -0400

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