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Encoding NaN in JSON

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  Encoding NaN in JSON Miki Tebeka <miki.tebeka@gmail.com> - 2013-04-16 17:21 -0700
    Re: Encoding NaN in JSON Tim Roberts <timr@probo.com> - 2013-04-16 22:38 -0700
      Re: Encoding NaN in JSON Miki Tebeka <miki.tebeka@gmail.com> - 2013-04-17 07:33 -0700
        Re: Encoding NaN in JSON John Gordon <gordon@panix.com> - 2013-04-17 14:47 +0000
        Re: Encoding NaN in JSON Johann Hibschman <jhibschman@gmail.com> - 2013-04-17 14:05 -0500
          Re: Encoding NaN in JSON Miki Tebeka <miki.tebeka@gmail.com> - 2013-04-17 14:21 -0700
            Re: Encoding NaN in JSON Roland Koebler <r.koebler@yahoo.de> - 2013-04-18 00:40 +0200
              Re: Encoding NaN in JSON Miki Tebeka <miki.tebeka@gmail.com> - 2013-04-17 18:01 -0700
                Re: Encoding NaN in JSON Roland Koebler <r.koebler@yahoo.de> - 2013-04-18 03:39 +0200
                Re: Encoding NaN in JSON Chris Angelico <rosuav@gmail.com> - 2013-04-18 11:41 +1000
                Re: Encoding NaN in JSON Chris Angelico <rosuav@gmail.com> - 2013-04-18 11:46 +1000
                Re: Encoding NaN in JSON Roland Koebler <r.koebler@yahoo.de> - 2013-04-18 10:11 +0200
          Re: Encoding NaN in JSON Dave Angel <d@davea.name> - 2013-04-17 17:37 -0400
        Re: Encoding NaN in JSON Wayne Werner <wayne@waynewerner.com> - 2013-04-18 08:53 -0500
          Re: Encoding NaN in JSON Grant Edwards <invalid@invalid.invalid> - 2013-04-19 14:54 +0000
            Re: Encoding NaN in JSON Chris “Kwpolska” Warrick <kwpolska@gmail.com> - 2013-04-19 20:21 +0200
              Re: Encoding NaN in JSON Grant Edwards <invalid@invalid.invalid> - 2013-04-19 19:42 +0000
                Re: Encoding NaN in JSON Chris “Kwpolska” Warrick <kwpolska@gmail.com> - 2013-04-20 10:00 +0200
                Re: Encoding NaN in JSON Wayne Werner <wayne@waynewerner.com> - 2013-04-22 13:53 -0500
        Re: Encoding NaN in JSON Tim Roberts <timr@probo.com> - 2013-04-18 22:04 -0700
          Re: Encoding NaN in JSON Robert Kern <robert.kern@gmail.com> - 2013-04-19 11:43 +0530
            Re: Encoding NaN in JSON Miki Tebeka <miki.tebeka@gmail.com> - 2013-04-19 12:52 -0700

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#43721 — Encoding NaN in JSON

Greetings,

I'm trying to find a way to have json emit float('NaN') as 'N/A'.
I can't seem to find a way since NaN is a float, which means overriding "default" won't help.

Any simple way to do this?

Thanks,
--
Miki

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#43730

Miki Tebeka <miki.tebeka@gmail.com> wrote:
>
>I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>I can't seem to find a way since NaN is a float, which means overriding "default" won't help.
>
>Any simple way to do this?

No.  There is no way to represent NaN in JSON.  It's simply not part of the
specification.  From RFC 4627 section 2.4:

   Numeric values that cannot be represented as sequences of digits
   (such as Infinity and NaN) are not permitted.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

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#43762

>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
> No.  There is no way to represent NaN in JSON.  It's simply not part of the
> specification.
I know that. I'm trying to emit the *string* 'N/A' for every NaN.

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#43764

In <c37a3b9c-6fe8-48aa-b703-9b4f922c3969@googlegroups.com> Miki Tebeka <miki.tebeka@gmail.com> writes:

> >> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
> > No.  There is no way to represent NaN in JSON.  It's simply not part of the
> > specification.
> I know that. I'm trying to emit the *string* 'N/A' for every NaN.

import math

x = possibly_NaN()

if math.isnan(x):
    x = 'N/A'

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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#43776

Miki Tebeka <miki.tebeka@gmail.com> writes:

>>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>> No.  There is no way to represent NaN in JSON.  It's simply not part of the
>> specification.
> I know that. I'm trying to emit the *string* 'N/A' for every NaN.

Easiest way is probably to transform your object before you try to write
it, e.g.

  def transform(x):
      if isinstance(x, dict):
          return dict((k, transform(v)) for k, v in x.items())
      elif isinstance(x, list) or isinstance(x, tuple):
          return [transform(v) for v in x]
      elif isinstance(x, float) and x != x:
          return 'N/A'
      else:
          return x

Then just use

  json.dumps(transform(x))

rather than just

  json.dumps(x)

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#43779

> >>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
> Easiest way is probably to transform your object before you try to write
Yeah, that's what I ended up doing. Wondered if there's a better way ...

Thanks,
--
Miki

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#43785

Hi,

> > Easiest way is probably to transform your object before you try to write
> Yeah, that's what I ended up doing. Wondered if there's a better way ...
yes, there is: subclass+extend the JSON-encoder, see pydoc json.

e.g.:
class JsonNanEncoder(json.JSONEncoder):
    def default(self, obj):
	if some-check-if-obj-is-NaN:
	    return 'NaN'
	return json.JSONEncoder.default(self, obj)

Roland

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#43791

[Roland]
> yes, there is: subclass+extend the JSON-encoder, see pydoc json.
Please read the original post before answering. What you suggested does not work since NaN is of float type.

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#43795

Hi,

> > yes, there is: subclass+extend the JSON-encoder, see pydoc json.
> Please read the original post before answering. What you suggested does not work since NaN is of float type.
ok, right, default does not work this way.
But I would still suggest to extend the JSON-encoder, since that is
quite simple (see sourcecode of JSON module); as a quickhack, you
could even monkey patch json.encoder.floatstr with a wrapper which
returns "N/A" for NaN. (I've tested it: It works.)

But: If you only need NaN and inf, and are ok with 'NaN' instead of 'N/A',
you can simply use the json module. See pydoc json:

    If allow_nan is True, then NaN, Infinity, and -Infinity will be
    encoded as such.  This behavior is not JSON specification compliant,
    but is consistent with most JavaScript based encoders and decoders.
    Otherwise, it will be a ValueError to encode such floats.

>>> import json
>>> json.dumps(float('NaN'))
'NaN'
>>> json.dumps(float('inf'))
'Infinity'


Roland

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#43796

On Thu, Apr 18, 2013 at 11:01 AM, Miki Tebeka <miki.tebeka@gmail.com> wrote:
> [Roland]
>> yes, there is: subclass+extend the JSON-encoder, see pydoc json.
> Please read the original post before answering. What you suggested does not work since NaN is of float type.

You may be able to override a bit more of the code, though. Check out
Lib/json/encoder.py for the implementation, and have a look at the
floatstr() internal function; unfortunately you can't simply subclass
and override that, but perhaps overriding iterencode (which is where
floatstr is defined) would do the job.

ChrisA

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#43797

On Thu, Apr 18, 2013 at 11:39 AM, Roland Koebler <r.koebler@yahoo.de> wrote:
> as a quickhack, you
> could even monkey patch json.encoder.floatstr with a wrapper which
> returns "N/A" for NaN. (I've tested it: It works.)

Wait... you can do that? It's internal to iterencode, at least in
Python 3.3 and 2.7 that I'm looking at here. Can you share your code
please? I'd like to try that! When I first looked at the docstring, I
was thinking "Ah, can I override the bit that emits NaN to return
\"N/A\" instead?", but the code made me think that's not possible.

ChrisA

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#43810

On Thu, Apr 18, 2013 at 11:46:37AM +1000, Chris Angelico wrote:
> Wait... you can do that? It's internal to iterencode, at least in
> Python 3.3 and 2.7 that I'm looking at here.
In Python 2.6 it wasn't internal to iterencode; in Python 2.7 and 3.x
you probably would have to monkey-patch iterencode. (In addition, patching
floatstr alone wouldn't be enough in 3.x and probably 2.7, since you also
have to make sure that the C-extension is not used here.)

BUT: Keep in mind that monkey-patches are problematic, and should be
avoided (or used very carefully) in production code. So, better
replace the complete encoder.py or use your own patched version
of the complete json-module.

Roland

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#43781

On 04/17/2013 03:05 PM, Johann Hibschman wrote:
> Miki Tebeka <miki.tebeka@gmail.com> writes:
>
>>>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>>> No.  There is no way to represent NaN in JSON.  It's simply not part of the
>>> specification.
>> I know that. I'm trying to emit the *string* 'N/A' for every NaN.
>
> Easiest way is probably to transform your object before you try to write
> it, e.g.
>
>    def transform(x):
>        if isinstance(x, dict):
>            return dict((k, transform(v)) for k, v in x.items())
>        elif isinstance(x, list) or isinstance(x, tuple):
>            return [transform(v) for v in x]
>        elif isinstance(x, float) and x != x:
>            return 'N/A'
>        else:
>            return x
>

Note that for a self-referencing object, this function might run 
"forever," or until it runs out of stack.  The programmer is likely to 
know about the possibility, but just in case ...

> Then just use
>
>    json.dumps(transform(x))
>
> rather than just
>
>    json.dumps(x)
>


-- 
DaveA

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#43829

On Wed, 17 Apr 2013, Miki Tebeka wrote:

>>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>> No.  There is no way to represent NaN in JSON.  It's simply not part of the
>> specification.
> I know that. I'm trying to emit the *string* 'N/A' for every NaN.

Why not use `null` instead? It seems to be semantically more similar...

-W

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#43903

On 2013-04-18, Wayne Werner <wayne@waynewerner.com> wrote:
> On Wed, 17 Apr 2013, Miki Tebeka wrote:
>
>>>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>>> No.  There is no way to represent NaN in JSON.  It's simply not part of the
>>> specification.
>> I know that. I'm trying to emit the *string* 'N/A' for every NaN.
>
> Why not use `null` instead? It seems to be semantically more similar...

Why not use 'NaN' instead? It seems to be even more semantically
similar...

-- 
Grant Edwards               grant.b.edwards        Yow! I want a VEGETARIAN
                                  at               BURRITO to go ... with
                              gmail.com            EXTRA MSG!!

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#43925

On Fri, Apr 19, 2013 at 4:54 PM, Grant Edwards <invalid@invalid.invalid> wrote:
> On 2013-04-18, Wayne Werner <wayne@waynewerner.com> wrote:
>> On Wed, 17 Apr 2013, Miki Tebeka wrote:
>>
>>>>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>>>> No.  There is no way to represent NaN in JSON.  It's simply not part of the
>>>> specification.
>>> I know that. I'm trying to emit the *string* 'N/A' for every NaN.
>>
>> Why not use `null` instead? It seems to be semantically more similar...
>
> Why not use 'NaN' instead? It seems to be even more semantically
> similar...

Because there is no NaN in JSON?  Unless you mean a string, which
makes no semantical sense and is human-oriented and not
machine-oriented.

--
Kwpolska <http://kwpolska.tk> | GPG KEY: 5EAAEA16
stop html mail                | always bottom-post
http://asciiribbon.org        | http://caliburn.nl/topposting.html

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#43933

On 2013-04-19, Chris ???Kwpolska??? Warrick <kwpolska@gmail.com> wrote:
> On Fri, Apr 19, 2013 at 4:54 PM, Grant Edwards <invalid@invalid.invalid> wrote:
>> On 2013-04-18, Wayne Werner <wayne@waynewerner.com> wrote:
>>> On Wed, 17 Apr 2013, Miki Tebeka wrote:
>>>
>>>>>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>>>>> No.  There is no way to represent NaN in JSON.  It's simply not part of the
>>>>> specification.
>>>> I know that. I'm trying to emit the *string* 'N/A' for every NaN.
>>>
>>> Why not use `null` instead? It seems to be semantically more similar...
>>
>> Why not use 'NaN' instead? It seems to be even more semantically
>> similar...
>
> Because there is no NaN in JSON?  Unless you mean a string, which
> makes no semantical sense and is human-oriented and not
> machine-oriented.

The OP asked for a string, and I thought you were proposing the string
'null'.  If one is to use a string, then 'NaN' makes the most sense,
since it can be converted back into a floating point NaN object.

I infer that you were proposing a JSON null value and not the string
'null'?

-- 
Grant Edwards               grant.b.edwards        Yow! I'm receiving a coded
                                  at               message from EUBIE BLAKE!!
                              gmail.com            

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#43952

On Fri, Apr 19, 2013 at 9:42 PM, Grant Edwards <invalid@invalid.invalid> wrote:
> The OP asked for a string, and I thought you were proposing the string
> 'null'.  If one is to use a string, then 'NaN' makes the most sense,
> since it can be converted back into a floating point NaN object.
>
> I infer that you were proposing a JSON null value and not the string
> 'null'?

Not me, Wayne Werner proposed to use the JSON null value.  I parsed
the backticks (`) used by him as a way to delimit it from text and not
as a string.

PS.
> On 2013-04-19, Chris ???Kwpolska??? Warrick <kwpolska@gmail.com> wrote:

Is Unicode support so hard, especially in the 21st century?

--
Kwpolska <http://kwpolska.tk> | GPG KEY: 5EAAEA16
stop html mail                | always bottom-post
http://asciiribbon.org        | http://caliburn.nl/topposting.html

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#44104

[Multipart message — attachments visible in raw view] — view raw

On Sat, 20 Apr 2013, Chris “Kwpolska” Warrick wrote:

> On Fri, Apr 19, 2013 at 9:42 PM, Grant Edwards <invalid@invalid.invalid> wrote:
>> The OP asked for a string, and I thought you were proposing the string
>> 'null'.  If one is to use a string, then 'NaN' makes the most sense,
>> since it can be converted back into a floating point NaN object.
>>
>> I infer that you were proposing a JSON null value and not the string
>> 'null'?
>
> Not me, Wayne Werner proposed to use the JSON null value.  I parsed
> the backticks (`) used by him as a way to delimit it from text and not
> as a string.

That was, in fact, my intention. Though it seems to me that you'll have to 
suffer between some sort of ambiguity - in Chrome, at least, 
`Number(null)` evaluates to `0` instead of NaN. But `Number('Whatever')` 
evaluates to NaN. However, a JSON parser obviously wouldn't be able to 
make the semantic distinction, so I think you'll be left with whichever 
API makes the most sense to you:

     NaN maps to null

            or

     NaN maps to "NaN" (or any other string, really)


Obviously you're not limited to these particular choices, but they're 
probably the easiest to implement and communicate.

HTH,
-W

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#43884

Miki Tebeka <miki.tebeka@gmail.com> wrote:
>
>>> I'm trying to find a way to have json emit float('NaN') as 'N/A'.
>> No.  There is no way to represent NaN in JSON.  It's simply not part of the
>> specification.
>
>I know that. I'm trying to emit the *string* 'N/A' for every NaN.

You understand that this will result in a chunk of text that is not JSON?
Other JSON readers won't be able to read it.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

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