jQuery $.param'ed string parsing in Python (app engine)

Question

I have a JavaScript dictionary that I want to pass to a Python app on app engine, put into datastore, retrieve from datastore and finally return as JSON. What's the right way to do it?

Say it looks something like that:

dict = {'box': 'huge',
        'crayons': [{ 'color': 'blue', 'l': 12 },
                    { 'color': 'red', 'l': 2 },
                    { 'color': 'yellow', 'l': 7 }]};

I serialize it using jQuery:

data = $.param(dict);

getting something like:

box=huge&crayons%5B0%5D%5Bcolor%5D=blue&crayons%5B0%5D%5Bl%5D=12&crayons%5B1%5D%5Bcolor%5D=red&crayons%5B1%5D%5Bl%5D=2&crayons%5B2%5D%5Bcolor%5D=yellow&crayons%5B2%5D%5Bl%5D=7

I send it using $.ajax to app engine (Python, Flask) and put it into datastore as a serialized string. Later I want to deserialize it to a Python dictionary and translate it to JSON using simplejson.

I have no idea how to deserialize it to a Python dictionary though.

Edit: Or maybe I'm doing it wrong and need to pass the dictionary to app engine differently?

Calvin · Accepted Answer · 2011-02-12 23:16:22Z

3

If you use $.param you lose type information when parsing the data. In your example the number 12 becomes the string '12'. Also boolean true would become string 'true'. This could lead to problems when you get the data back from the server.

If maintaining type information is important to you, you might want to json encode the object before sending it to app engine (https://github.com/douglascrockford/JSON-js). Then you could just put the data straight into the datastore and return it on request.

answered Feb 12, 2011 at 23:16

Calvin

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1 Comment

Mike Over a year ago

Looks promising! Might be exactly what I was missing. :) Thanks a lot!

Daniel Roseman · Accepted Answer · 2011-02-12 20:02:55Z

2

urlparse.parse_qs:

>>> import urlparse
>>> urlparse.parse_qs("box=huge&crayons%5B0%5D%5Bcolor%5D=blue&crayons%5B0%5D%5Bl%5D=12&crayons%5B1%5D%5Bcolor%5D=red&crayons%5B1%5D%5Bl%5D=2&crayons%5B2%5D%5Bcolor%5D=yellow&crayons%5B2%5D%5Bl%5D=7")
{'box': ['huge'],
'crayons[0][color]': ['blue'],
'crayons[0][l]': ['12'],
'crayons[1][color]': ['red'],
'crayons[1][l]': ['2'],
'crayons[2][color]': ['yellow'],
'crayons[2][l]': ['7']}

answered Feb 12, 2011 at 20:02

Daniel Roseman

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1 Comment

Mike Over a year ago

Thanks! Unfortunately being a Python and JSON noob I have trouble using it (when I generate json and pass it to jQuery I cannot address the items properly ('crayons[0][color]' is a full identifier and I need to use separate crayons[0], crayons[1] etc. objects. I'll probably end up writing a simple regex dealing with it, but I hoped for a more elegant solution. Oh well.

cce · Accepted Answer · 2011-06-16 03:42:26Z

1

Well urlparse.parse_qs is pretty nice, but if you have nested structures, etc, there is jquery-unparam which will further parse all those nested objects for you. It seems to work fairly well for me so far.

>>> from jquery_unparam import jquery_unparam
>>> jquery_unparam("a=1&b%5B%5D=2&b%5B%5D=3&b%5B%5D=4&c%5Bd%5D=5")
{'a': '1', 'c': {'d': '5'}, 'b': ['2', '3', '4']}

>>> from urlparse import parse_qs
>>> parse_qs("a=1&b%5B%5D=2&b%5B%5D=3&b%5B%5D=4&c%5Bd%5D=5")
{'a': ['1'], 'b[]': ['2', '3', '4'], 'c[d]': ['5']}

edited Jun 16, 2011 at 3:42

answered Jun 9, 2011 at 19:28

cce

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Comments

Adrian Lopez · Accepted Answer · 2014-06-27 21:53:28Z

0

Use JSON.stringify(dict) to serialize your JavaScript dictionary, and json.loads(dict_string) to deserialize into a Python dictionary.

Thus, your JavaScript code would look something like this:

$.ajax({
    url: '/some/url',
    type: 'post',
    data: { 
        'dict': JSON.stringify(dict) 
    }    
});

... and your Python code would look something like this:

import json

from google.appengine.ext import webapp

class MyRequestHandler(webapp.RequestHandler):
    def post(self):
        dict = json.loads(self.request.get('dict'))

answered Jun 27, 2014 at 21:53

Adrian Lopez

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neuron · Accepted Answer · 2011-02-12 19:47:55Z

-1

json.loads(request.POST)

That's from simplejson and how I do it in django.

answered Feb 12, 2011 at 19:47

neuron

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