jsonfield.py

from django.db import models
import json

class JSONField(models.TextField):
    def __init__(self, verbose_name=None, name=None, default=None, **kwargs):
        models.TextField.__init__(self, verbose_name, name, **kwargs)
        
    def to_python(self, value):
        if isinstance(value, six.string_types) or value is None:
            return value
        return json.loads(value)
        
    def value_to_string(self, obj):
      self.value_from_object(json.dumps(obj))