Django-rest-framework: DecimalField serialised as string

[0atman]

Ints are serialised correctly, but DecimalField is serialsed to String.

I don't think this is correct:

{
    "int field" : 1,
    "decimal_field": "0.00"
}

[0atman]

Same problem with FloatField. I've noticed there doesn't seem to be a DecimalField serializer.

[0atman]

Hmm, I might have been wrong when I said IntegerField was correct. It seems only ID is serialised to a JSON number.

[tomchristie]

Decimals need to be serialized as strings in JSON, since float representation would lose precision.
You end up with weird things like 0.1 -> 0.09999999999
Same approach taken in Django's fixtures.

Hmm, I might have been wrong when I said IntegerField was correct. It seems only ID is serialised to a JSON number.

If you can clarify feel free to open that as a separate issue. Not aware of any issue currently, but could be wrong.

[0atman]

Fixed-place decimals don't have the problem with precision, surely? That's why I'm using them in my application.

[tomchristie]

Fixed-place decimals don't have the problem with precision, surely?

They don't. Until they get converted to _binary_ floating point.

There's no such thing as a Decimal type in Javascript, so you need to use string reprs.

http://stackoverflow.com/questions/1960516/python-json-serialize-a-decimal-object

(And yeah I was a bit surprised the first time I realized it was so, too)

[0atman]

Lame! It looks like simplejson supports decimal exporting correctly, but that would add a dependency to DRF...

[tomchristie]

simplejson is bundled with Django.
Looking at this http://code.google.com/p/simplejson/issues/detail?id=34 seems like you can tweak the JSONRenderer to use use_decimal and things will work as you're hoping. It's likely you'll still lose precision on the other side of the wire, but still...

On 15 Dec 2012, at 12:41, Tristram Oaten [email protected] wrote:

Lame! It looks like simplejson supports decimal exporting correctly, but that would add a dependency to DRF...

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Reply to this email directly or view it on GitHub.

[lorinkoz]

Here's a problem with parsing decimals as string: If you're using AngularJs and bind a Django generated form with a DecimalField to an object coming from a DRF api, the initial object to form binding doesn't work, because the object property is a string and the field expects a numeric type. Any way to work this around?

[tomchristie]

3.0 gives you the option to serialize decimals as floats.

https://github.com/tomchristie/django-rest-framework/blob/version-3.0/docs/topics/3.0-announcement.md#decimals-as-strings-in-serializer-data

REST_FRAMEWORK = {
    'COERCE_DECIMAL_TO_STRING': False
}

[maryokhin]

By the way, we have the opposite need, to serialize IDs as strings, because Javascript doesn't support 64-bit integers. Is there a pretty way to do this (apart from matching *_id field names in renderer)?

[tomchristie]

Quick and dirty: use the renderer as you suggest. Fuller: override ModelSerializer, creating a new base class that gives you a string based relation field for relationships. The API for allowing users to make that kind of customization isn't really done yet tho.

[lorinkoz]

Thanks for answering. Are you planning to make version 3.x available on PyPi anytime soon?

[tomchristie]

Are you planning to make version 3.x available on PyPi anytime soon?

Yes. It'll be coming shortly.