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serialize text field to json

a third-party application I am using is storing json in a textfield.
I would like to serialize this data to json, and I only need to be able to read from this serializer, not write to it. I don't want to have to manipulate the data on the frontend, so I want it to come out at clean json from my api.
class SomeSerializer(serializers.ModelSerializer):
details = serializers.CharField()
class Meta:
model = SomeModel
fields = ( 'id', 'details')
right now this is returning:
[{"id":"someID",
"details":"{\"address\": {\"city\": null}"}"}]
I can't figure out how to use json.loads in a serializer, which would seem the cleanest option.

You can use SerializerMethodField.
import json
from rest_framework import serializers
class SomeSerializer(serializers.ModelSerializer):
details = serializers.SerializerMethodField()
class Meta:
model = SomeModel
fields = ('id', 'details')
def get_details(self, obj):
return json.loads(obj.details)
Note that SerializerMethodField is read_only, cannot for write.

How to serialize Inherited models in Django REST Framework

I'm working on a Django Rest Framework project, in which I have created the following models as:
from django.db import models
# Base Models...
choices = (
('Single', 'Single'),
('Multiple', 'Multiple'),
)
class UserAccountModel(models.Model):
deployment_name = models.CharField(max_length=150, blank=True)
credentials = models.FileField(upload_to='media/credentials/', name='credentials'),
project_name = models.CharField(max_length=150, blank=True)
project_id = models.CharField(max_length=100, blank=False, name='project_id')
cluster_name = models.CharField(max_length=150, blank=False)
zone_region = models.CharField(max_length=150, blank=False)
services = models.CharField(max_length=100, choices=choices)
def __str__(self):
return self.deployment_name
class AwdModel(UserAccountModel):
source_zip = models.FileField(upload_to='media/awdSource/', name='awd_source')
routing = models.TextField(name='routing', null=True)
def __str__(self):
return self.deployment_name
def save(self, **kwargs):
if not self.id and self.services == 'Multiple' and not self.routing:
raise ValidationError("You must have to provide routing for multiple services deployment.")
super().save(**kwargs)
# def clean(self):
# if self.services == 'Multiple' and self.routing is None:
# raise ValidationError('You must have to provide routing for multiple services deployment.')
class AwodModel(UserAccountModel):
source_zip = models.FileField(upload_to='media/awodSource/', name='awod_source')
routing = models.TextField({'type': 'textarea'}, name='routing')
def save(self, **kwargs):
if not self.id and self.services == 'Multiple' and not self.routing:
raise ValidationError("You must have to provide routing for multiple services deployment.")
super().save(**kwargs)
I need to serialize these models, Here's how I have implemented serializers for these models:
from rest_framework import serializers
from .models import UserAccountModel, AwdModel, AwodModel
class UserAccountSerializer(serializers.ModelSerializer):
class Meta:
model = UserAccountModel
fields = ('deployment_name', 'credentials', 'project_name',
'project_id', 'cluster_name', 'zone_region', 'services')
class AWDSerializer(serializers.ModelSerializer):
class Meta(UserAccountSerializer.Meta):
model = AwdModel
fields = UserAccountSerializer.Meta.fields + ('awd_source', 'routing',)
class AWODSerializer(serializers.ModelSerializer):
class Meta:
model = AwodModel
fields = '__all__'
But, when I try to access, AWDSerialzer it return an error as:
AttributeError at /api/v1/deployments/
Got AttributeError when attempting to get a value for field project_id on serializer AWDSerializer.
The serializer field might be named incorrectly and not match any attribute or key on the QuerySet instance.
Original exception text was: 'QuerySet' object has no attribute 'project_id'.
Update: Here's my APIView code:
class DeploymentsList(APIView):
def get(self, request):
MAX_OBJECTS = int(20)
deployments = AwdModel.objects.all()[:MAX_OBJECTS]
data = AWDSerializer(deployments).data
return Response(data)
class DeploymentDetail(APIView):
def get(self, request, *args, **kwargs):
deployment = get_object_or_404(AwdModel, pk=kwargs['pk'])
data = AWDSerializer(deployment).data
return Response(data)
Help me, please!
Thanks in advance!

AttributeError at /api/v1/deployments/ Got AttributeError when
attempting to get a value for field project_id on serializer
AWDSerializer. The serializer field might be named incorrectly and not
match any attribute or key on the QuerySet instance. Original
exception text was: 'QuerySet' object has no attribute 'project_id'.
This is an attribute error, when attempting to get the value from field project_id .
Get rid of the name attribute in the project_id field.
Edit The APIView code
To serialize a queryset or list of objects instead of a single object
instance, you should pass the many=True flag when instantiating the
serializer. You can then pass a queryset or list of objects to be
serialized. [Serializing multiple objects]
class DeploymentsList(APIView):
def get(self, request):
MAX_OBJECTS = int(20)
deployments = AwdModel.objects.all()[:MAX_OBJECTS]
data = AWDSerializer(deployments, many=True).data
return Response(data)
I hope this will help.

The code that you posted appears to be valid and correct. The issue however is unrelated. The exception text 'QuerySet' object has no attribute 'project_id' Refers to an issue that likely originates from your restframework app's views.py file. The exception states that you are attempting to access the attribute 'project_id' from a QuerySet.
A QuerySet is a (lazy loaded) set of models and not a single model. Even if the query set had only one element you'd still be required to access that element before accessing it's attributes.
Because you haven't shared your views.py file I can't say for sure where the issue is however here is an incorrect use case example: MyModel.objects.all().project_id. Here we can see that I am attempting to access the attribute project_id from a query set. A correct use case would be MyModel.objects.all()[0].project_id. However this assumes that the query set is not empty.
Practically, most DjangoRestFramework views inherit from rest_framework.views.APIView which subclasses django's View Class. I would suggest checking the query_set within that class is being used correctly.
Feel free to share your implementation here for further comment.
[EDIT] - After views.py coded was added.
You are attempting to serializer an entire query set with the instantiation of a serializer data = AWDSerializer(deployments).data this is causing the attribute error.
I would recommend the generics.ListAPIView class and the use of the class attributes query_set and serializer_class. These are simple to implement. You can then invoke the APIViews default get method. Here is an example for your DeploymentsList view
from rest_framework import generics
class DeploymentsList(generics.ListAPIView):
serializer_class = AWDSerializer
queryset = AwdModel.objects.all()
def get(self, request, *args, **kwargs):
MAX_OBJECTS = int(20)
self.queryset = self.queryset[:MAX_OBJECTS]
return super(DeploymentsList, self).get(request, *args, **kwargs)
[EDIT] - FileField Serialization
In order to serialize the UserAccount.credentials file field so that we serializer the path, we can use the serializers.SerializerMethodField. I.e Your UserAccountSerializer becomes:
class UserAccountSerializer(serializers.ModelSerializer):
credentials = serializers.SerializerMethodField()
def get_credentials(self, user_account):
return user_account.credentials.path
class Meta:
model = UserAccountModel
fields = ('deployment_name', 'credentials', 'project_name',
'project_id', 'cluster_name', 'zone_region', 'services')

When you inherit from a model class which is not defined as abstract in it’s own meta class, then Django creates a one-to-one relation between the subclass and its parent. Which actually creates two tables in the database; one for the base class and one for the subclass.
I haven’t tried your code, nor used Django 2, but would check using a relational field between the two serializer.

Django rest framework posting expects dictionary

I am trying to post to my API with foreign key relationships. It's throwing me back an error saying it's expecting a dictionary as opposed to int for character, character_opponent and stage. This is because the way my models are set up. They have foreign key relationships. The model in question looks like this:
import uuid
from django.db import models
from django.utils import timezone
from analysis.models import Analysis
from characters.models import Character
from stages.models import Stage
class Match(models.Model):
analysis = models.ForeignKey(Analysis, on_delete=models.CASCADE)
character = models.ForeignKey(Character, on_delete=models.CASCADE, related_name='character')
character_won = models.BooleanField()
character_opponent = models.ForeignKey(Character, on_delete=models.CASCADE, related_name='character_opponent')
character_opponent_won = models.BooleanField()
created_at = models.DateTimeField(editable=False)
id = models.UUIDField(primary_key=True, default=uuid.uuid4)
updated_at = models.DateTimeField(editable=False)
stage = models.ForeignKey(Stage, on_delete=models.CASCADE)
def __str__(self):
return '%s vs. %s on %s' % (self.character, self.character_opponent, self.stage)
def save(self, *args, **kwargs):
''' On save, update timestamps '''
if not self.created_at:
self.created_at = timezone.now()
self.updated_at = timezone.now()
return super(Match, self).save(*args, **kwargs)
class Meta:
db_table = "matches"
And here is my serializer:
from rest_framework import serializers
from matches.models import Match
from characters.serializers import CharacterSerializer
from stages.serializers import StageSerializer
class MatchSerializer(serializers.ModelSerializer):
character = CharacterSerializer()
character_opponent = CharacterSerializer()
stage = StageSerializer()
class Meta:
model = Match
fields = ('id', 'analysis', 'character', 'character_won', 'character_opponent', 'character_opponent_won', 'stage')
Is there some option I am missing here to be able to post properly? Clearly I shouldn't have to pass the entire character object each time I want to post something, right? I should just be able to pass the primary key.

From your few comments I understood that you need nested serializer in GET method. What I suggest is, use two[or more] serializers for your API class.
Assuming you are using ModelViewSet API class is using,then you could override get_serializer_class() method as below,
from rest_framework.viewsets import ModelViewSet
class MatchAPI(ModelViewSet):
queryset = Match.objects.all()
def get_serializer_class(self):
if self.action == 'create':
return MatchCreateSerializer
return MatchSerializer
And your MatchCreateSerializer will be like this,
class MatchCreateSerializer(serializers.ModelSerializer):
class Meta:
fields = '__all__'
model = Match
Thus, you only need to provide the PKs of analysis,character etc while creation of Match instance

It will come down to your CharacterSerializer and StageSerializer. If you want to input 1 format (using serialisers.PrimaryKeyRelatedField()), but output another (CharacterSerializer, StageSerializer), you might be best served using 2 serialisers and switching in your view.
In your view you can override get_serializer_class and check your request method, or in the case of a viewset you can check the method being invoked.

When you declare a serializer related field using another serializer, like this
character = CharacterSerializer()
you are telling django-rest-framework that you want a nested serializer. What you want is something like this instead
character = serializers.PrimaryKeyRelatedField()
or you can actually just leave the explicit field declaration out of the serializer (since this is the default), see the doc on serializer relations.

Property field in a django model is not serialized. How to fix?

I have the following model:
def get_file_path(instance, filename):
return 'files/{0}/{1}'.format(instance.user.username, filename)
class File(models.Model):
fid = models.UUIDField(primary_key=True, default=uuid.uuid4)
user = models.ForeignKey(settings.AUTH_USER_MODEL)
file = models.FileField(upload_to=get_file_path)
when I try to serialize this model using for example serializers.serialize('json', File.objects.all()) I get:
u'[{"model": "app_name.file", "pk": "45f616b4-d028-488e-83c5-878ce1028018", "fields": {"user": 1, "file": "files/username/filename.txt"}}]'
I want the serialized json to also include the file field's url which file_obj.file.url returns so I added a property field like so:
class File(models.Model):
fid = models.UUIDField(primary_key=True, default=uuid.uuid4)
user = models.ForeignKey(settings.AUTH_USER_MODEL)
file = models.FileField(upload_to=get_file_path)
def _get_file_url(self):
"Returns file's url"
return self.file.url
url = property(_get_file_url)
However property field url is still not serialized. So I tried to write a custom serializer for the model by extending serializers.ModelSerializer like so:
class FileSerializer(serializers.ModelSerializer):
class Meta:
model = File
fields = ('fid', 'user', 'file', 'url')
which doesn't work and I get 'module' object has no attribute 'ModelSerializer'. is it because django doesn't have ModelSerializer class and only django rest_framwork does ? if so how do I solve this if I am using django only and not django rest framework ?
Thanks.

when not using DRF - what is a poor idea...
you have to build manually in your view the dict with the data you wish to return and then use from django.http.response import JsonResponse for serializing the result.
def single_object_representation(obj):
return {
'fid': obj.fid,
'user': obj.user.username,
'url': obj._get_file_url()
}
def demo_view(request):
objects_to_serialize = File.objects.all()
result = [single_object_representation(obj) for obj in objects_to_serialize]
return JsonResponse(result, safe=False)
using django.core.serializers
see here: https://docs.djangoproject.com/en/2.0/topics/serialization/#subset-of-fields
but make sure it will work with your property. For some fields like User you should use duble underscore notation __ e.g user__username
otherwise (with DRF) - what I strongly recommend to you
First of all install drf:
pip install djangorestframework
Then if there is still problem with your serializer give a try to the SerializerMethodField (if in doubt see the docs: http://www.django-rest-framework.org/api-guide/fields/#serializermethodfield)
from rest_framework import serializers
class FileSerializer(serializers.ModelSerializer):
url = serializers.SerializerMethodField()
class Meta:
model = File
fields = ('fid', 'user', 'file', 'url')
def get_url(self):
return self. _get_file_url()

Using __init__ in django to annotate a model with extra information

I wrote an __init__ method for one of my models that adds some auxiliary information to the object by dynamically adding an attribute to the object that does not reflect a column in the database:
class MyModel(models.Model):
title = Models.CharField()
description = Models.TextField()
def __init__(self, *args, **kwargs):
self.aux_info = "I'm not in the database!"
This seemed to be working fine, but I found a case where it does not work. I have some code in a view where I set a status variable and package up a list of MyModels into json like so:
from django.core import serializers
from django.utils import simplejson
...
# have to use serializers for django models
serialized_items = serializers.serialize("json", itemlist)
data["items"] = serialized_items # serialized_items is now a string
data["status"] = status
# package up data dict using simplejson for python objects
resp = simplejson.dumps(data)
return HttpResponse(resp, mimetype="application/javascript")
The problem seems to be that django's serializers only serialize the model fields and not all attributes of the object so aux_info does not come through. I'm also pretty sure that using both serializers and simplejson is not the right way to do this. Thanks for any help!

Try usung the serialiser's optional fields argument.
serialized_items = serializers.serialize("json", itemlist, fields=['.....', 'aux_info'])
May i also suggest that using the __init__ method to add fields is considdered bad form in django and would be much better achieved like so:
class MyModel(models.Model):
title = Models.CharField()
description = Models.TextField()
def aux_info(self):
return "I'm not in the database!"