Thread: [Pyparsing] jsonParser.py patch

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Hi all,

I've changed the jsonParser.py example from the distro to accommodate
top-level arrays (as of RFC4627, http://tools.ietf.org/html/rfc4627).
Please find the patch attached.

Cheers,
Thomas

Your attachment was stripped somewhere along the way.  Could you please
paste it to a http://pyparsing.pastebin.com/?

Thanks,
-- Paul 

-----Original Message-----
From: pyp...@li...
[mailto:pyp...@li...] On Behalf Of thomas_h
Sent: Tuesday, April 22, 2008 10:35 AM
To: pyp...@li...
Subject: [Pyparsing] jsonParser.py patch

Hi all,

I've changed the jsonParser.py example from the distro to accommodate
top-level arrays (as of RFC4627, http://tools.ietf.org/html/rfc4627).
Please find the patch attached.

Cheers,
Thomas

Done. It's at http://pyparsing.pastebin.com/m2c33d08d, if that is of
help. Thanks for the hints.

Thomas

On Tue, Apr 22, 2008 at 6:40 PM, Paul McGuire <pt...@au...> wrote:
> Your attachment was stripped somewhere along the way.  Could you please
>  paste it to a http://pyparsing.pastebin.com/?
>
>  Thanks,
>  -- Paul
>
>
>
>  -----Original Message-----
>  From: pyp...@li...
>  [mailto:pyp...@li...] On Behalf Of thomas_h
>  Sent: Tuesday, April 22, 2008 10:35 AM
>  To: pyp...@li...
>  Subject: [Pyparsing] jsonParser.py patch
>
>  Hi all,
>
>  I've changed the jsonParser.py example from the distro to accommodate
>  top-level arrays (as of RFC4627, http://tools.ietf.org/html/rfc4627).
>  Please find the patch attached.
>
>  Cheers,
>  Thomas
>
>

Thomas -

Hrm, well, I can see that this works, but I'm not sold.  A jsonObject really
*isn't* a choice between a jsonDict and a jsonArray.  It really is a '{'
members '}', as per the BNF.  I think the real problem is elsewhere.

The RFC link you gave was very helpful.  It states that the content of the
JSON string can be any JSON value, which you tripped over because you
encountered a JSON array when we were parsing for a JSON object.

The solution is not to change the definition of jsonObject.  The solution is
that we should have been invoking this:

jsonValue.parseString(testdata)

not this:

jsonObject.parseString(testdata)

which was my mistake in the original code.  Not thinking, I assumed that
JSON object was the all-encompassing type, but JSON value is what we are
really being given.

jsonValue already encompasses checking for all the different JSON value
types - not just object and array, but also number, true, false, etc.  Try
reverting to the original jsonParser.py, but change this statement instead
and see if you get successful parsing.  (You may find that the results are
nested an extra level deep, you'll have to pick out element [0] of the data
returned from parseString.)

I'll fix this in the next release (coming soon, I hope)!

Cheers,
-- Paul

-----Original Message-----
From: pyp...@li...
[mailto:pyp...@li...] On Behalf Of thomas_h
Sent: Tuesday, April 22, 2008 2:43 PM
To: pyp...@li...
Subject: Re: [Pyparsing] jsonParser.py patch

Done. It's at http://pyparsing.pastebin.com/m2c33d08d, if that is of help.
Thanks for the hints.

Thomas

On Tue, Apr 22, 2008 at 6:40 PM, Paul McGuire <pt...@au...> wrote:
> Your attachment was stripped somewhere along the way.  Could you 
> please  paste it to a http://pyparsing.pastebin.com/?
>
>  Thanks,
>  -- Paul
>
>
>
>  -----Original Message-----
>  From: pyp...@li...
>  [mailto:pyp...@li...] On Behalf Of 
> thomas_h
>  Sent: Tuesday, April 22, 2008 10:35 AM
>  To: pyp...@li...
>  Subject: [Pyparsing] jsonParser.py patch
>
>  Hi all,
>
>  I've changed the jsonParser.py example from the distro to accommodate  
> top-level arrays (as of RFC4627, http://tools.ietf.org/html/rfc4627).
>  Please find the patch attached.
>
>  Cheers,
>  Thomas
>
>

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Paul,

>  Hrm, well, I can see that this works, but I'm not sold.  A jsonObject really
>  *isn't* a choice between a jsonDict and a jsonArray.  It really is a '{'
>  members '}', as per the BNF.  I think the real problem is elsewhere.

Yes, I wasn't very happy with my naming but I'm not very good at
naming anyway and I thought it would do. 'jsonObject' should probably
be reserved for what I named 'jsonDict', and what I named 'jsonObject'
should be called something else.

>  The RFC link you gave was very helpful.  It states that the content of the
>  JSON string can be any JSON value, which you tripped over because you
>  encountered a JSON array when we were parsing for a JSON object.

I read this too, but wasn't sure I could trust my understanding.
Especially after I ran my current "reference implementation" (demjson)
on a file containing just "this is a value", which was dismissed as
illegal.

The RFC defines (if I get it right) 'JSON-text' as the start symbol
and says "A JSON text is a serialized object or array.

      JSON-text = object / array".

That might speak in favor of my approach. I think the BNF (I presume
you are referring to the sidebar of json.org) supports your
understanding as well since there is no dedicated start symbol.
(Actually, I can't find that text again where it says JSON is just a
JSON value ...).

>
>  The solution is not to change the definition of jsonObject.  The solution is
>  that we should have been invoking this:
>
>  jsonValue.parseString(testdata)

Fair enough. It might be overgenerating, though.

>  jsonValue already encompasses checking for all the different JSON value
>  types - not just object and array, but also number, true, false, etc.  Try
>  reverting to the original jsonParser.py, but change this statement instead
>  and see if you get successful parsing.

I'm sure this will work, I'll give it a try.

Keep up,
Thomas

Yes, I was too quick to read that part of the RFC, I was working just off
the content of json.org, which is a bit squishier on the format then the RFC
is.

If what we will get is JSON-text, then let's just call it jsonText, and
define it as:

jsonText = jsonObject | jsonArray
jsonText.ignore(jsonComment)

print jsonText.parseString(testdata)

And we should be confident now that jsonText matches the JSON-Text from the
RFC.

-- Paul

-----Original Message-----
From: pyp...@li...
[mailto:pyp...@li...] On Behalf Of thomas_h
Sent: Tuesday, April 22, 2008 4:47 PM
To: Paul McGuire
Cc: pyp...@li...
Subject: Re: [Pyparsing] jsonParser.py patch

Paul,

>  Hrm, well, I can see that this works, but I'm not sold.  A jsonObject 
> really
>  *isn't* a choice between a jsonDict and a jsonArray.  It really is a '{'
>  members '}', as per the BNF.  I think the real problem is elsewhere.

Yes, I wasn't very happy with my naming but I'm not very good at naming
anyway and I thought it would do. 'jsonObject' should probably be reserved
for what I named 'jsonDict', and what I named 'jsonObject'
should be called something else.

>  The RFC link you gave was very helpful.  It states that the content 
> of the  JSON string can be any JSON value, which you tripped over 
> because you  encountered a JSON array when we were parsing for a JSON
object.

I read this too, but wasn't sure I could trust my understanding.
Especially after I ran my current "reference implementation" (demjson) on a
file containing just "this is a value", which was dismissed as illegal.

The RFC defines (if I get it right) 'JSON-text' as the start symbol and says
"A JSON text is a serialized object or array.

      JSON-text = object / array".

That might speak in favor of my approach. I think the BNF (I presume you are
referring to the sidebar of json.org) supports your understanding as well
since there is no dedicated start symbol.
(Actually, I can't find that text again where it says JSON is just a JSON
value ...).

>
>  The solution is not to change the definition of jsonObject.  The 
> solution is  that we should have been invoking this:
>
>  jsonValue.parseString(testdata)

Fair enough. It might be overgenerating, though.

>  jsonValue already encompasses checking for all the different JSON 
> value  types - not just object and array, but also number, true, 
> false, etc.  Try  reverting to the original jsonParser.py, but change 
> this statement instead  and see if you get successful parsing.

I'm sure this will work, I'll give it a try.

Keep up,
Thomas

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