How to make an object JSON-serializable?

[Cosmia Luna]

I want to to return some SQLAlchemy object to the json renderer, of course it didn't work.
Can I add a method to the Base like:

class Base(object):
    def __jsonSerialize__(self):
        pass # return a dict-like object

Base=declarative_base(cls=Base)

Or I have to write a renderer called ejson(extendable json renderer) or some other wrapping the default json renderer?

Thanks,
Cosmia

[Julien Cigar]

I wrote a basic json/xml serializer some time ago:
http://www.pastie.org/3496853
It's pretty basic and unfinished at all but .. if it can help

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[Robert Forkel]

I use a combination of this. A __json__ method on Base, and a custom json renderer, taking this method into account.
Regards
Robert

--

[Alexis Métaireau]

What I'm doing is to add a property on the models I want to serialize,
and to use a custom json serializer for this purpose.

Have a look at
https://github.com/spiral-project/ihatemoney/blob/master/budget/models.py#L12
and
https://github.com/ametaireau/flask-rest/blob/master/flask_rest.py#L144

However, this isn't automatic, and it is probably possible to automate
this without having to explicitly specify what you want to serialize
(like Julien did)

[Cosmia Luna]

Hmm... It seems that renderer doesn't have such a interface, but that's OK, because writing a renderer is so easy.

Thanks,
Cosmia

[Cosmia Luna]

May be you can try to look into the just add such a line to the base, it can help you get the list of defined properties of the model,

class Base(object):
    def __init__(self, *args, **kwargs):
        # do your business here
        self._to_serialize=self.__table__.columns.keys()
        # do some other thing or add other stuff you want to serialize

But it can only return those explicitly defined columns, properties won't be returned, you can add them later.

Regards,
Cosmia

[Cosmia Luna]

PS: I meant "you can try to look into the Base.__table__.columns object

Regards,
Cosmia

[John Anderson]

This is the code I use (if your e-mail doesn't preview code well: http://paste2.org/p/1921598):

    def serialize(self, localtz=None):

        """Converts all the properties of the object into a dict

        for use in json

        """

        props = {}

        def is_valid_key(key):

            if not key.startswith('_') and \

               not 'password' in key and \

               not 'salt' == key:

               return True

        _items = self.__class__.__dict__

        local_at = dict()

        if _items.has_key('timezone') and (getattr(self, 'timezone') or localtz):

            timezone = localtz or getattr(self,'timezone')

            if _items.has_key('start_time') and getattr(self,'start_time'):

                local_at.update(self._localize_time('start_date', 'start_time', timezone.name))

            if _items.has_key('end_time') and getattr(self,'end_time'):

                local_at.update(self._localize_time('end_date', 'end_time', timezone.name))

        for key, value in _items.items():

            if is_valid_key(key):

                obj = getattr(self, key)

                if hasattr(obj, 'serialize'):

                    props[key] = obj.serialize()

                elif not callable(obj):

                    if isinstance(obj, datetime) or isinstance(obj, date):

                        _date = local_at.get(key,None) or obj

                        props[key] = _date.strftime("%Y-%m-%d")

                    elif isinstance(obj, time):

                        _time = local_at.get(key,None) or obj

                        props[key] = _time.strftime("%I:%M %p")

                    else:

                        props[key] = getattr(self, key)

        props['id'] = str(self.pk)

        return props

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[Andrey Popp]

Sorry for self-advertisement, but I've wrote a small utility to solve this kind
of problems -- jsonpublish[1]. Code looks like this:

class Base(object):
pass

from jsonpublish import register_adapter, dumps

@register_adapter(Base)
def adapt_base(b):
return {} # adapt Base object to json-encodable structure

dumps(Base()) # now it works!

See docs[1] for more info.

[1]: http://jsonpublish.readthedocs.org/en/latest/index.html