DRF local variable 'msg_data' referenced before assignment - django

Question

This is my serializers.py
class UserProfileSerializer(serializers.ModelSerializer):
img_count = serializers.SerializerMethodField('get_img_count')
post_count = serializers.SerializerMethodField('get_post_count')
msg_count = serializers.SerializerMethodField('get_msg_count')
class Meta:
model = User
fields = ('id', 'username', 'img_count', 'post_count', 'msg_count')
def get_img_count(self, obj):
try:
img_data = ImgSerializer(Img.objects.filter(author=obj.id), many=True)
except img_data.DoesNotExist:
return 0
return img_data
def get_post_count(self, obj):
try:
post_data = PostSerializer(Post.objects.filter(author=obj.id), many=True)
except post_data.DoesNotExist:
return 0
return post_data
def get_msg_count(self, obj):
try:
msg_data = Smessage(Msg.objects.filter(author=obj.id), many=True)
except msg_data.DoesNotExist:
return 0
return msg_data
This is my views.py
class UserProfile(APIView):
permission_classes = [AllowAny]
def get(self, request):
query = User.objects.all()
serializer = UserProfileSerializer(query, many=True)
return Response(serializer.data)
This is the Error Snippet
I want to get this
{
"id": 9,
"username": "emil#gmail.com",
"img_count:3,
"post_count":5,
"msg_count":50,
}
also getting error after using img_count.count().

Answer 1

You should change the exceptions to:
img_data.DoesNotExist --> Img.DoesNotExist
post_data.DoesNotExist --> Post.DoesNotExist
msg_data.DoesNotExist --> Msg.DoesNotExist
Because, instances does not have any exception object, rather the model classes has them. More information can be found in documentation.
Update
If you just want the count, then you don't need to use such extensive implementation. You can simply try:
def get_img_count(self, obj):
return Img.objects.filter(author=obj.id).count()
def get_post_count(self, obj):
return Post.objects.filter(author=obj.id).count()
def get_msg_count(self, obj):
return Msg.objects.filter(author=obj.id).count()

Answer 2

You should set default value of each variable because in case of error other than DoesNotExist, you will face this error.
class UserProfileSerializer(serializers.ModelSerializer):
img_count = serializers.SerializerMethodField('get_img_count')
post_count = serializers.SerializerMethodField('get_post_count')
msg_count = serializers.SerializerMethodField('get_msg_count')
class Meta:
model = User
fields = ('id', 'username', 'img_count', 'post_count', 'msg_count')
def get_img_count(self, obj):
img_data = 0
try:
img_data = ImgSerializer(Img.objects.filter(author=obj.id), many=True).data
except Img.DoesNotExist:
pass
return img_data
def get_post_count(self, obj):
post_data = 0
try:
post_data = PostSerializer(Post.objects.filter(author=obj.id), many=True).data
except Post.DoesNotExist:
pass
return post_data
def get_msg_count(self, obj):
msg_data = 0
try:
msg_data = Smessage(Msg.objects.filter(author=obj.id), many=True).data
except Msg.DoesNotExist:
pass
return msg_data