How to parse a list of class objects from json text in python?

Question

I use the json library to decode json text

import json

I have a Party class defined like this:

class Party(object):
    id = ""
    code = ""
    create_date = ""
    citizenship = ""

an object_hook method:

def as_party(d):
    p = Party()
    p.__dict__.update(d)
    return p

I can use this method in order to get a Party object from a json text:

def parse_as(s, typo_class):
    return json.loads(str(s), object_hook=typo_class)

When I call the parse_as method on a json text containing encoded Party class, i get an object of type Party.

json_text = {'id': 2, 'code': '2', 'create_date': null, 'citizenship': null}
party1 = parse_as(json_text, as_party)

I can call its attributes like this:

print party1.code

My problem is to make the parse_as method able to parse a json text containing a list of Party objects like this one:

json_text = [{'id': 2, 'code': '2', 'create_date': null, 'citizenship': null}, {'id': 5, 'code': '3', 'create_date': null, 'citizenship': null}, {'id': 6, 'code': '8', 'create_date': null, 'citizenship': null}]

Please help me and thanks in advance!

vertazzar · Accepted Answer · 2014-08-28 17:42:57Z

2

object hook needs to be changed

def as_party(d):
    if isinstance(d, dict):
      p = Party()
      p.__dict__.update(d)
    elif isinstance(d, list):
     out = []
     for i in d:
       n = Party()
       n.__dict__.update(i)
       out.append(n)
     p = out
    else:
      raise Exception('got non-dict value %s' % d)
    return p

btw, i wouldnt use __dict__, would rather use setattr with some prefix...

because if key value is a python keyword, that wont be good.

>>> a = Foo()
>>> a.__dict__['except'] = 1
>>> a.except
  File "<stdin>", line 1
    a.except
           ^
SyntaxError: invalid syntax

edited Aug 28, 2014 at 17:42

answered Aug 28, 2014 at 17:37

vertazzar

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1 Comment

Oussama Over a year ago

Thank you for the solution :) Can you explain your other alternative (using setattr) ?

vertazzar · Accepted Answer · 2014-08-29 20:45:10Z

as for different approach using setattr and avoiding colision of python keywords you can use:

def as_party(d):
    if isinstance(d, dict):
      p = Party()
      for k,v in d.iteritems():
        setattr(p, 'v_%s' % k, v) # you can assign any prefix you want
    elif isinstance(d, list):
     out = []
     for i in d:
       n = Party()
       for k,v in i.iteritems():
         setattr(n, 'v_%s' % k, v)
       out.append(n)
     p = out
    else:
      raise Exception('got non-dict value %s' % d)
    return p

but then you would have to access those values with prefix that we incorporated like so:

print party.v_for, party.v_except # etc..

generally, you could work out the code that it does not allow python keywords:

import keyword

def as_party(d):
    if isinstance(d, dict):
      p = Party()
      for k,v in d.iteritems():
        if keyword.iskeyword(k):
          raise Exception('Cannot accept %s as a property name. That is resrved python keyword' % k)
        setattr(p, k, v) # you can assign any prefix you want
    elif isinstance(d, list):
     out = []
     for i in d:
       n = Party()
       for k,v in i.iteritems():
        if keyword.iskeyword(k):
          raise Exception('Cannot accept %s as a property name. That is resrved python keyword' % k)
         setattr(n, k, v)
       out.append(n)
     p = out
    else:
      raise Exception('got non-dict value %s' % d)
    return p

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