Passing a JSON object through POST using Python

Question

I'm trying to post a JSON object through a POST. I'm trying to do it as follows:

import json, urllib, urllib2

filename = 'test.json'
race_id = 2530
f = open(filename, 'r')
fdata = json.loads(f.read())
f.close()

prefix = 'localhost:8000'

count = 0
for points in fdata['positions'].iteritems():
    print '--' + str(count) + '--------'
    url = 'http://'+prefix+'/api/points'
    parameters = {'point_data': json.dumps(points), 'race_id': race_id}
    data = urllib.urlencode(parameters)
    print data
    request = urllib2.Request(url, data)
    response = urllib2.urlopen(request)
    count += 1
    break;

print 'Finished adding points'

The data is then received on the other end (I'm using Google App Engine) with:

point_data = json.load(self.request.get('point_data'))

But I get the following error:

ERROR    2010-06-30 15:08:05,367
__init__.py:391] 'unicode' object has no attribute 'read' Traceback (most
recent call last):   File
"/home/ian/workspace/google_appengine/google/appengine/ext/webapp/__init__.py",
line 513, in __call__
    handler.post(*groups)   File "/home/ian/workspace/codebase/track_builder/geo-api.py",
line 276, in post
    point_data = json.load(self.request.get('point_data'))
File
"/home/ian/workspace/google_appengine/lib/django/django/utils/simplejson/__init__.py",
line 208, in load
    return cls(encoding=encoding, **kw).decode(fp.read()) AttributeError: 'unicode' object has
no attribute 'read' INFO    
2010-06-30 15:08:05,376
dev_appserver.py:3266] "POST
/api/points HTTP/1.1" 500 -

Any ideas on how to fix this?

EDIT: As requested here is an example of the points:

(u'1276859700',
{
    u'24': {
        u'tempc': u'-22.7',
        u'gpsq': u'1',
        u'altm': u'65527',
        u'hd': u'112',
        u'hdop': u'0.93',
        u'bton': u'0',
        u'maxv': u'20.15',
        u'idit': u'1',
        u'satc': u'10',
        u'minv': u'20.15',
        u'lat': u'35.271993',
        u'btusr': u'0',
        u'lng': u'-121.845353',
        u'knots': u'7'
    },
    u'11': {
        u'tempc': u'13.0',
        u'gpsq': u'1',
        u'altm': u'65535',
        u'hd': u'130',
        u'hdop': u'0.84',
        u'bton': u'0',
        u'maxv': u'15.96',
        u'idit': u'1',
        u'satc': u'12',
        u'minv': u'15.88',
        u'lat': u'34.877815',
        u'btusr': u'0',
        u'lng': u'-121.386116',
        u'knots': u'8'
    }
}

EDIT 2: Thanks to Daniel Roseman and Nick Johnson who both caught my error. I've changed

point_data = json.loads(self.request.get('point_data'))

This has solved the error but, now I'm getting:

ERROR    2010-06-30 16:07:29,807 __init__.py:391] 'list' object has no attribute 'iteritems'
Traceback (most recent call last):
  File "/home/ian/workspace/google_appengine/google/appengine/ext/webapp/__init__.py", line 513, in __call__
    handler.post(*groups)
  File "/home/ian/workspace/codebase/track_builder/geo-api.py", line 255, in post
    for time, units in point_data.iteritems():
AttributeError: 'list' object has no attribute 'iteritems'
INFO     2010-06-30 16:07:29,816 dev_appserver.py:3266] "POST /api/points HTTP/1.1" 500 -

which relates to the following code:

class TrackPoint(webapp.RequestHandler):
    def post(self):
        point_data = json.loads(self.request.get('point_data'))
        race_id = self.request.get('race_id')
        added = []
        failed = []
        for time, units in point_data.iteritems():
            for unit, data in units.iteritems():
                ...

Any ideas on this one?

Answer 1

It looks like self.request.get() is returning a unicode object rather than a file-like object. You could try using json.loads() instead of json.load().

Answer 2

json.load() expects a file object, but self.request.get returns the value of the parameter as a string.

The solution is easy: use json.loads.

Also, free tip: I presume from the name that you're bundling your own copy of the json library. App Engine actually includes a copy of simplejson that you can use - just do:

from django.utils import simplejson

Answer 3

first in js I recognize that json object must in STRING format (javascript file)

// using jquery, json2
var js = {"name":"nguyen","age":"1"};
$.post("/", {'data': JSON.stringify(js)}, function(ret){
        alert(ret);
    });

then in gae

from django.utils import simplejson as json

class PesonReq(webapp.RequestHandler):
    def post(self):
        t = json.loads(self.request.POST['data'])
        self.response.out.write(t['name'])