I am learning Django. I wrote a simple model and some views method in Django rest framework so that I can modify some particular attributes when needed to all the records that need that. Here is the model:
from django.db import models
class Category(models.Model):
name = models.CharField(max_length=255)
isActive = models.BooleanField(default=True)
def __str__(self):
return self.name
Then, I created this view to modify the isActive session when I call it:
class CategoriesChangeActiveView(views.APIView):
def post(self, request, format=None):
try:
categories = request.data.get('categories')
for category in categories:
category = Category.objects.get(id=category['id'])
category.isActive = category['isActive']
category.save()
except Exception as e:
return Response({'error': 'Bad request'}, status=status.HTTP_400_BAD_REQUEST)
return Response({'success': 'Active changed'}, status=status.HTTP_200_OK)
Even when the format of my request is correct ( I debugged each line ) when it comes to the line category.isActive = category['isActive']it throws the error that'Category' object is not subscriptable`. I don't know why or how to fix it.
I saw in the official documentation, on older StackOverflow questions that this is doable, but I don't understand why I can't.
Can someone please suggest what I am doing wrong? Thank you
it's a simple mistake.
Simply change it as follows and it should be fixed:
categories = request.data.get('categories')
for category in categories:
category_obj = Category.objects.get(id=category['id'])
category_obj.isActive = category['isActive']
category_obj.save()
What you're doing is changing what the variable category is. You for loop and the unpacked variable is category, but then you get the model object and set the variable as category
So initially, the category variable is in fact a dictionary object, but you change it to be a django model object instance.
Specifically, the issue is here:
category = Category.objects.get(id=category['id'])
category.isActive = category['isActive']
You set category to be an instance of the Category model (which in this case corresponds to a db record, but that bit is a little irrelevant).
Accessing attributes on a class instance is not done by the square bracket notation, but rather dot notation.
So instead of category['isActive'] use category.isActive
If category was a dictionary, eg.
category = {
"name": "cat",
"isActive": True,
}
Then you would use the square bracket notation as category["isActive"] to get that value.
As it is, it's not a dict, so python thinks you are trying to subscript the instance somehow, which will not work.
Related
Hello django developers !. I hope you all are fine.. :)
Well here i want to get the shop_owner from shop detail view to the get context data function so i can count the total products of that particular shop..
models.py
class ShopProfile(models.Model):
shop_owner = models.OneToOneField(User, related_name='shop_profile', on_delete=models.CASCADE)
shop_address = models.CharField(_("shop address"), max_length=255)
views.py
class ShopProfileDetailView(DetailView):
model = ShopProfile
template_name='shops/shop_profile.html'
def get_context_data(self,*args, **kwargs):
context = super(ShopProfileDetailView, self).get_context_data(*args, **kwargs)
user = context['shop_owner'] #getting error here
context["products_count"] = Product.objects.filter(product_owner=user).count()
return context
If the KeyError is raised from a failed dictionary key lookup in your own code, you can use . get() to return either the value found at the specified key or a default value.
Well I fixed it, By printing the context variable above the error line, in my case
print('context data',context)
user = context['shop_owner'] #getting error here
It will return some fields in the terminal then You can simply get any data from that context. :)
I have two apps menu and table. In app table, I have this model:
class Table(models.Model):
available = models.BooleanField(verbose_name="Availability", default=True)
def set_availability(self, avail=False):
self.fields['available'] = avail
self.save()
def __str__(self):
return "Table " + str(self.id_num)
In one of the views of app menu, I have the following call:
from table.models import Table
def menu_category_view(request, table_pk):
table = Table.objects.get(pk=table_pk)
if table.available:
table.set_availability(False)
...
return render(request,
...)
When my template calls this view, I receive this error message 'Table' object has no attribute 'fields'. Here, I am trying to update the value of field available of the instance being called (from True to False). And I got this implementation suggested from a book. Is this the right way to update model instance field value? Thanks.
Just set the attribute.
def set_availability(self, avail=False):
self.available = avail
self.save()
Though, it's questionable whether or not set_<field> methods like this are particularly useful. You could work with the object almost as easily:
if table.available:
table.available = False
table.save()
I am trying to build a single course platorm where I will only hold lessons units materials where only people with membership will be able to see it , however when I try to do retrieve Lesson.course_allowed_mem_types.all() I got the following error 'ManyToManyDescriptor' object has no attribute 'all' , how can I fix this simple error?
class Lesson(models.Model):
content_title = models.CharField(max_length=120)
content_text = models.CharField(max_length=200)
thumbnail = models.ImageField(upload_to='static/xxx/xxx/xxx/xxx')
link = models.CharField(max_length=200, null=True)
allowed_memberships = models.ManyToManyField(Membership)
def __str__(self):
return self.content_title
views
def get_context_data(self, **kwargs):
context = super(bootCamp, self).get_context_data(**kwargs)
context['lessons'] = Lesson.objects.all()
user_membership = UserMembership.objects.filter(user=self.request.user).first()
user_membership_type = user_membership.membership.membership_type
course_allowed_mem_types = Lesson.allowed_memberships.all()
context['course_allowed_mem_types'] = course_allowed_mem_types
return context
You can query many-to-many related field only for model instance, not model class. It's not really clear what exactly is "all concrete allowed membership objects for a Lesson class" (Lesson.allowed_memberships.all()).
Is it "all membership objects related to any of existing lesson objects" or is it "all membership objects that can be related to a lesson object"?
Those are different queries, and Lesson.allowed_memberships.all() does not imply either, it's incorrect usage.
If you want the former, something like this could work
Membership.objects.filter(lesson__in=Lesson.objects.all())
(You already have this as context['lessons'] so use that instead, just showing the idea)
I think,
One lesson may have many memberships. so you are selecting all lessons with all memberships Lesson.allowed_memberships.all() .
Try selecting a single lesson then retrieve associated members
lesson = Lessons.objects.filter(pk=1)
course_allowed_mem_types = lesson.allowed_memberships.all()
If you want to create custom list like type, it is always a good idea to inherit from collections.abc.Iterable. It provides common operations required to work on such container types.
You can't just call .all() on any object/type, that type definition actually has to have all() method defined in class or parent class.
e.g.
class ListLike:
def __init__(self):
...
def all(self):
return some_iterator
I have 3 models, Run, RunParameter, RunValue:
class Run(models.Model):
start_time = models.DateTimeField(db_index=True)
end_time = models.DateTimeField()
class RunParameter(models.Model):
parameter = models.ForeignKey(Parameter, on_delete=models.CASCADE)
class RunValue(models.Model):
run = models.ForeignKey(Run, on_delete=models.CASCADE)
run_parameter = models.ForeignKey(RunParameter, on_delete=models.CASCADE)
value = models.FloatField(default=0)
class Meta:
unique_together=(('run','run_parameter'),)
A Run can have a RunValue, which is a float value with the value's name coming from RunParameter (which is basically a table containing names), for example:
A RunValue could be AverageTime, or MaximumTemperature
A Run could then have RunValue = RunParameter:AverageTime with value X.
Another Run instance could have RunValue = RunParameter:MaximumTemperature with value Y, etc.
I created an endpoint to query my API, but I only have the RunParameter ID (because of the way you can select which parameter you want to graph), not the RunValue ID directly. I basically show a list of all RunParameter and a list of all Run instances, because if I showed all instances of RunValue the list would be too long and confusing, as instead of seeing "Maximum Temperature" you would see:
"Maximum Temperature for Run X"
"Maximum Temperature for Run Y"
"Maximum Temperature for Run Z", etc. (repeat 50+ times).
My API view looks like this:
class RunValuesDetailAPIView(RetrieveAPIView):
queryset = RunValue.objects.all()
serializer_class = RunValuesDetailSerializer
permission_classes = [IsOwnerOrReadOnly]]
And the serializer for that looks like this:
class RunValuesDetailSerializer(ModelSerializer):
run = SerializerMethodField()
class Meta:
model = RunValue
fields = [
'id',
'run',
'run_parameter',
'value'
]
def get_run(self, obj):
return str(obj.run)
And the URL just in case it's relevant:
url(r'^run-values/(?P<pk>\d+)/$', RunValuesDetailAPIView.as_view(), name='values_list_detail'),
Since I'm new to REST API, so far I've only dealt with having the ID of the model API view I am querying directly, but never an ID of a related field. I'm not sure where to modify my queryset to pass it an ID to get the appropriate model instance from a related field.
At the point I make the API query, I have the Run instance ID and the RunParameter ID. I would need the queryset to be:
run_value = RunValue.objects.get(run=run_id, run_parameter_id=param_id)
While so far I've only ever had to do something like:
run_value = RunValue.objects.get(id=value_id) # I don't have this ID
If I understand correctly, you're trying to get an instance of RunValue with only the Run id and the RunParameter id, i.e. query based on related fields.
The queryset can be achieved with the following:
run_value = RunValue.objects.get(
run__id=run_id,
run_parameter__id=run_parameter_id
)
Providing that a RunValue instance only ever has 1 related Run and RunParameter, this will return the instance of RunValue you're after.
Let me know if that's not what you mean.
The double underscore allows you to access those related instance fields in your query.
Well its pretty simple, all you have to do is override the get_object method, for example(copy pasted from documentation):
# view
from django.shortcuts import get_object_or_404
class RunValuesDetailAPIView(RetrieveAPIView):
queryset = RunValue.objects.all()
serializer_class = RunValuesDetailSerializer
permission_classes = [IsOwnerOrReadOnly]]
lookup_fields = ["run_id", "run_parameter_id"]
def get_object(self):
queryset = self.get_queryset() # Get the base queryset
queryset = self.filter_queryset(queryset) # Apply any filter backends
filter = {}
for field in self.lookup_fields:
if self.kwargs[field]: # Ignore empty fields.
filter[field] = self.kwargs[field]
obj = get_object_or_404(queryset, **filter) # Lookup the object
self.check_object_permissions(self.request, obj)
return obj
# url
url(r'^run-values/(?P<run_id>\d+)/(?P<run_parameter_id>\d+)/$', RunValuesDetailAPIView.as_view(), name='values_list_detail'),
But one big thing you need to be careful, is not to have duplicate entries with same run_id and run_parameter_id, then it will throw errors. To avoid it, either use unique_together=['run', 'run_parameter'] or you can use queryset.filter(**filter).first() instead of get_object_or_404 in the view. But second option will produce wrong results when duplicate entries are created.
I have two tabels(Ingredient_Step and Ingredient) in on relation as you can see below:
Models.Py
class Ingredient_Step(models.Model):
ingredient = models.ForeignKey(Ingredient)
Step = models.ForeignKey(Step)
def __unicode__(self):
return u'{}'.format(self.Step)
class Ingredient(models.Model):
IngredientName = models.CharField(max_length=200,unique=True)
Picture = models.ImageField(upload_to='Ingredient')
def __unicode__(self):
return u'{}'.format(self.IngredientName)
In a function, i need serialize a JSON object from a query that returns from "Ingredient_step", but I need send the field "IngredientName", who comes from "Ingredient" table.
I try using "ingredient__IngredientName" but it fails.
Views.Py:
def IngredientByStep(request):
if request.is_ajax() and request.GET and 'id_Step' in request.GET:
if request.GET["id_Step"] != '':
IngStp = Ingredient_Step.objects.filter(Step =request.GET["id_Step"])
return JSONResponse(serializers.serialize('json', IngStp, fields=('pk','ingredient__IngredientName')))
How i can call extends field from a relation?
Thanks
This "feature" of Django (and many ORM's like SQLAlchemy) are called Lazy Loading, meaning data is only loaded from related models if you specifically ask for them. In this case, build your IngStp as a list of results, and make sure to access the property for each result before serializing.
Here's an example of how to do that: Django: Include related models in JSON string?