Type error trying to load fixtures with Content_type natural keys in Django

Question

I am using the --natural option when dumping one of my model into a fixtures, so that I won't run into Content_typ ID problem when deploying. Results is here:

{
     "pk": 1, 
     "model": "seo.opportunitymetadatamodel", 
     "fields": {
         "_content_type": [
              "opportunity", 
              "jobopportunity"
         ], 
         "og_description": "", 
         "description": "", 
         "title": "test", 
         "keywords": "", 
         "og_title": "", 
         "heading": ""
     }
}

But when I try to load back the fixture, I get the following error:

Problem installing fixture 'seo/fixtures/initial_data.json': Traceback (most recent call last):
  File "/Users/xx/dev/envs/xx/lib/python2.6/site-packages/django/core/management/commands/loaddata.py", line 167, in handle
    for obj in objects:
  File "/Users/xx/dev/envs/xx/lib/python2.6/site-packages/django/core/serializers/json.py", line 38, in Deserializer
    for obj in PythonDeserializer(simplejson.load(stream), **options):
  File "/Users/xx/dev/envs/xx/lib/python2.6/site-packages/django/core/serializers/python.py", line 84, in Deserializer
    Model = _get_model(d["model"])
TypeError: string indices must be integers, not str

Seems like the method does not accept a string to load. What am I missing ?

Answer 1

I can only guess right now, but after looking at Django's source code and your error message I think the format of your fixture might be broken. The example you posted, is that the whole content of the file? If yes, then I think you need to put that model in a list, like this (pay attention to the outer brackets):

[
  {
    "pk": 1, 
    "model": "seo.opportunitymetadatamodel", 
    "fields": {
      "_content_type": [
        "opportunity", 
        "jobopportunity"
      ], 
      "og_description": "", 
      "description": "", 
      "title": "test", 
      "keywords": "", 
      "og_title": "", 
      "heading": ""
    }
  }
]

---

Why? After Django parsed the JSON data successfully, this data is passed to the python deserializer. This iterates over the data as follows:

82      for d in object_list:
83          # Look up the model and starting build a dict of data for it.
84          Model = _get_model(d["model"])

http://code.djangoproject.com/browser/django/trunk/django/core/serializers/python.py#L82

Now imagine object_list is a json object (equivalent to python's dictionary), iterating over it will only get you the keys, in this case pk, model, field. In line 84 Django does _get_model(d["model"]), that is, using a string "model" as index to another string, probably pk (which is the first element in object_list). That's a type error.

When object_list is an actual list, iterating over it will give you dictionaries, which can be indexed by strings.