Django: Converting an entire set of a Model's objects into a single dictionary

Question

If you came here from Google looking for model to dict, skip my question, and just jump down to the first answer. My question will only confuse you.

Is there a good way in Django to entire set of a Model's objects into a single dictionary? I mean, like this:

class DictModel(models.Model):
    key = models.CharField(20)
    value = models.CharField(200)


DictModel.objects.all().to_dict()

... with the result being a dictionary with the key/value pairs made up of records in the Model? Has anyone else seen this as being useful for them?

Thanks.

Update
I just wanted to add is that my ultimate goal is to be able to do a simple variable lookup inside a Template. Something like:

{{ DictModel.exampleKey }}

With a result of DictModel.objects.get(key__exact=exampleKey).value

Overall, though, you guys have really surprised me with how helpful allof your responses are, and how different the ways to approach it can be. Thanks a lot.

Update October 2011: This question is the top result if you Google "django model_to_dict", which is actually pretty awful given that it solves a different problem than what I was asking.

What I wanted was to be able to map all of the instances in a queryset into a single dictionary with a specified model field as the key.
model_to_dict, on the other hand converts a single model instance into a dictionary.

Now, my needs at the time were pretty darn specific, and probably extremely rare (I can't even remember the project I needed it for, or why). So I would be pretty surprised that anyone looking for information about model_to_dict is going to find my question actually useful. Sorry.

model_to_dict seems to be a much more common usage case than I had.

Update Dec 2011:
I changed the title to hopefully better reflect my original intent.

Solution 1

Does this need to create an actual dict? could you get by with only something that looked like a dict?

class DictModelAdaptor():
    def __init__(self, model):
        self.model = model

    def __getitem__(self, key):
        return self.model.objects.get(key=key)

    def __setitem__(self, key, item):
        pair = self.model()
        pair.key = key
        pair.value = item
        pair.save()

    def __contains__(self, key):
        ...

You could then wrap a model in this way:

modelDict = DictModelAdaptor(DictModel)
modelDict["name"] = "Bob Jones"

etc...

Solution 2

You can also rely on django code already written ;).

from django.forms.models import model_to_dict
model_to_dict(instance, fields=[], exclude=[])

Solution 3

You are looking for the Values member of QuerySet which allows you to get a list of dictionaries from your query

Returns a ValuesQuerySet -- a QuerySet that evaluates to a list of dictionaries instead of model-instance objects. Each of those dictionaries represents an object, with the keys corresponding to the attribute names of model objects.

>>> Blog.objects.values()
[{'id': 1, 'name': 'Beatles Blog', 'tagline': 'All the latest Beatles news.'}],
>>> Blog.objects.values('id', 'name')
[{'id': 1, 'name': 'Beatles Blog'}]

Solution 4

You want the in_bulk queryset method which, according to the docs:

Takes a list of field values (id_list) and the field_name for those values, and returns a dictionary mapping each value to an instance of the object with the given field value. If id_list isn’t provided, all objects in the queryset are returned. field_name must be a unique field, and it defaults to the primary key.

It takes a list of IDs, so you'll need to get that first via the values_list method:

ids = MyModel.objects.values_list('id', flat=True)
ids_to_model_instances = MyModel.objects.in_bulk(ids)
# {1: <MyModel: 1>, 2: <MyModel: 2>, 3: <MyModel: 3>}

Solution 5

You can use the python serializer:

from django.core import serializers
data = serializers.serialize('python', DictModel.objects.all())

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