datetime.date is not JSON serializable

[carlo]

I had this problem trying to serialize a (SQLite) date field with
simplejson through "js.dumps(mydata)" :

File "C:\Python25\web2py\gluon\contrib\simplejson\encoder.py", line
332, in default
raise TypeError("%r is not JSON serializable" % (o,))
TypeError: datetime.date(2009, 1, 14) is not JSON serializable

It seems something similar happened in Django:

http://code.djangoproject.com/ticket/2460

Is there any workaround?

carlo

[Timothy Farrell]

That's funny, I just dealt with this issue yesterday. I'll put a tip on
the wiki and link it.

-tim

--
Timothy Farrell <tfar...@swgen.com>
Computer Guy
Statewide General Insurance Agency (www.swgen.com)

[carlo]

Thank you Tim, I am looking forward to it.

carlo

On 14 Gen, 18:18, Timothy Farrell <tfarr...@swgen.com> wrote:
> That's funny, I just dealt with this issue yesterday.  I'll put a tip on
> the wiki and link it.
>
> -tim
>
>
>
> carlo wrote:
> > I had this problem trying to serialize a (SQLite) date field with
> > simplejson  through "js.dumps(mydata)" :
>
> > File "C:\Python25\web2py\gluon\contrib\simplejson\encoder.py", line
> > 332, in default
> >     raise TypeError("%r is not JSON serializable" % (o,))
> > TypeError: datetime.date(2009, 1, 14) is not JSON serializable
>
> > It seems something similar happened in Django:
>
> >http://code.djangoproject.com/ticket/2460
>
> > Is there any workaround?
>
> > carlo
>
> --

> Timothy Farrell <tfarr...@swgen.com>

[Timothy Farrell]

BAM!

https://mdp.cti.depaul.edu/web2py_wiki/default/wiki/JSONdatetime

--
Timothy Farrell <tfar...@swgen.com>

[mdipierro]

fantastic. can you email me a patch?
does it work for date and time too?

[carlo]

very interesting, thank you!

carlo

[Timothy Farrell]

Yes, it works for date but it does not work for time. I'm not sure how
this would look implemented into web2py. (You should read the page more
thoroughly.)

-Tim

--
Timothy Farrell <tfar...@swgen.com>

[achipa]

I believe json doesn't do this by default for at least a couple of
reasons

a) the solution would be programming language/version/application
specific
b) you can't differentiate strings from dates as json has no metadata
on it's fields
c) you'd have to stick to a RFC style complicated date parser to avoid
regional (=date format) problems

I actually made a patch for this myself, but it's much more cludgy
(that's why I didn't post it here), in my solution made the field look
like TIMESTAMP#TZ and added a #DATE to the key name (since I load it,
too, a hook removes this and recreates the date object transparently).

[Timothy Farrell]

Did you look at my implementation?

1) Yes, this is a problem, but we can't get around it when we still need
a solution. My solution works for Python 2.5 and 2.6 and the dates are
supported in all major, modern browsers.
2) My implementation doesn't use strings in a JSON object. It relies on
the JSON parser parsing the JSON as a Javascript engine would.
3) My implementation doesn't parse a timestamp string, rather it builds
a Javascript date object using the date. That should be a little more
cross-locale (is that the right term?)

-tim

--
Timothy Farrell <tfar...@swgen.com>

[achipa]

Yes, I've taken a brief look

1) agreed
2) I got the impression the 'new Date..' is stored as string in the
JSON object, and thus it would be indistinguishable from a regular
string field with the same content, but if it's just for eval-ing, it
works (although I always get goosebumps when I see code in JSON, the
next iteration of ecma is introducing parsejson() instead of eval()
for exactly this reason). I guess it's about choice.
3) it's ok, as long as you don't use/care about TZ

[Timothy Farrell]

3) Good point. Currently all of our customers are (should be) in the
same timezone. That may need some adjustment in the future.

--
Timothy Farrell <tfar...@swgen.com>

[carlo]

There is also a dates JQuery plugin which seems to be able to convert
a string date in a Date javascript object: this could be useful as you
can have Json serialize dates as strings and then convert them to
javascript Date objects. Anyone tried it?

carlo