[storm] How to JSON encode a item from a ResultSet

[Mario Zito]

Jamu:
Ok, it works with VERY minor corrections:

The resulting code is:

*def encode_storm_object(object):*
*     if not hasattr(object, "__storm_table__"):*
*         raise TypeError(repr(object) + " is not JSON serializable")*
*
*
*     result = {}*
*     cls_info = get_cls_info(object.__class__)*
*     for name in cls_info.attributes.iterkeys():*
*         result[name] = getattr(object, name)*
*     return result*

Only errors were "hassattr" with two "ss" and "__storm_table" corrected to
"__storm_table__"

Thanks again !
Mario

2010/5/27 Jamu Kakar <jkakar at kakar.ca>

> Hi Mario,
>
> On Thu, May 27, 2010 at 10:14 PM, Mario Zito <mazito at analyte.com> wrote:
> > I would like to iterate over all items of a returned ResultSet encoding
> each
> > one using JSON. Example code follows:
> > class Topic(object):
> >     __storm_table__= "Trancos.topic"
> >     id = Int(primary=True)
> >     account_id= Int()
> >     title= Unicode()
> >     properties= Unicode()
> >     notes= Unicode()
> >     # and other attrs not important here ...
>
> 8< snip
>
> >     rs= store.find(Topic)
> >     for t in rs:
> >         print t.id, json.dumps(t)
> > But I get the error:
> >   File "/usr/lib/python2.6/json/encoder.py", line 344, in default
> >     raise TypeError(repr(o) + " is not JSON serializable")
> > TypeError: <__main__.Topic object at 0x26f3090> is not JSON serializable
> >
> > Any ideas ? Is there a way to serialize a Storm object (or a full
> ResultSet)
> > to JSON ?
>
> You need to create a custom encoder for use with simplejson.  One
> way forward is to create a custom encoder for each of your Storm
> objects.  See the 'Specializing JSON object encoding' section in the
> simplejson documentation for more information [1].  Something like
> this should work (untested):
>
>  import simplejson
>
>  def encode_topic(topic):
>      if isinstance(topic, Topic):
>          return {"id": topic.id, "account_id": topic.account_id,
>                  "title": topic.title, "properties": topic.properties,
>                  "notes": topic.notes}
>      raise TypeError(repr(topic) + " is not JSON serializable")
>
>  print simplejson.dumps(topic, default=encode_complex)
>
> This will get tedious if you have many different kinds of objects to
> convert, so you might want to create a generic encoder function that
> will work with any Storm object, for example (also untested):
>
>  import simplejson as json
>  from storm.info import get_cls_info
>
>  def encode_storm_object(object):
>      if not hassattr(object, "__storm_table"):
>          raise TypeError(repr(object) + " is not JSON serializable")
>
>      result = {}
>      cls_info = get_cls_info(object.__class__)
>      for name in cls_info.attributes.iterkeys():
>          result[name] = getattr(object, name)
>      return result
>
>  storm_object = get_storm_object()
>  print simplejson.dumps(storm_object, default=encode_storm_object)
>
> This won't dump non-Storm fields though, which may or may not be a
> problem depending on your needs.  Hopefully it's enough to get you
> started doing what you want.
>
> Thanks,
> J.
>
> [1]
> http://simplejson.googlecode.com/svn/tags/simplejson-2.1.1/docs/index.html
>



-- 
Mario A. Zito
ANALYTE SRL
Parana 457, piso 2, of. 'A'
(C1033AAI) Buenos Aires, Argentina
tel: (54-11) 5258-0205 int 138
mazito at analyte.com
www.analyte.com
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