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'Category' object is not subscriptable Django

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.

How can I set an attribute to use in both POST and GET methods in django class-based views?

So I'm building a class-based view that uses data from a table on my db, both on POST and GET methods. I've been trying to set an attribute with the table to mitigate the time that it would take to pull the table again for the sake of performance.
Because of how functions/methods work I can't set an attribute like this:
class MyClass (View):
#md(login_required(login_url='login',redirect_field_name=None))
def get(self, request):
con = create_engine('mysql+mysqlconnector://user:password#localhost:8000/schema')
#function to get a dict with db tables
tabs = get_tables(con)
#Trying to make the attribute
self.table = tabs['table_That_I_need']
context{'data':tabs}
return render(request, 'markowitz/markowitz.html',context)
#md(login_required(login_url='login',redirect_field_name=None))
def post(self, request):
#this gives me an error since the attribute was not set
table = self.table
form = MarkowitzForm(request.POST,table)
if form.is_valid():
pass
return render(request, 'markowitz/results.html')
I've been trying to use setattr but it doesn't seem to be working

With self.table = ... you are essentially setting the attribute on the current instance. And Django creates new instances for each request. Which means, the table attribute of one instance isn't shared with another instance.
What you want to do is to set the attribute on the MyClass itself:
def get(...):
...
if not hasattr(self.__class__, 'table'):
# set table attr if not already present
setattr(self.__class__, 'table', tabs['table_That_I_need'])
...

how can I fix ManyToManyDescriptor from a lesson class model - view?

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

Attaching extra information to model instance - django

I have a django model that I want to attach an extra piece of information to, depending on the environment the instance is in (which user is logged in). For this reason, I don't want to do it at the database level.
Is this okay to do? Or are there problems that I don't foresee?
in models.py
class FooOrBar(models.Model):
"""Type is 'foo' or 'bar'
"""
def __init__(self, type):
self.type = type
in views.py
class FooCheck(FooOrBar):
"""Never saved to the database
"""
def __init__(self, foo_or_bar):
self.__dict__ = foo_or_bar.__dict__.copy()
def check_type(self, external_type):
if external_type == 'foo':
self.is_foo = True
else:
self.is_foo = False
foos_or_bars = FooOrBar.objects.all()
foochecks = map(FooCheck, foos_or_bars)
for foocheck in foochecks:
foocheck.check_type('foo')
extra credit question: Is there a more efficient way of calling a method on multiple objects i.e. replacing the last forloop with something clever?

Okay, this does not work. Trying to delete a FooOrBar objects throws a complaint about
OperationalError at /
no such table: test_FooCheck
To get around this I'm just not going to inherit from FooOrBar, but if anyone has a suggestion on a better way to do it I'd be interested in hearing it

I had a similar issue, I did something like:
class Foo(models.Model):
# specific info goes here
class Bar(models.Model):
# specific info goes here
class FooBar(models.Model):
CLASS_TYPES = {
"foo":Foo,
"bar":Bar
}
type = models.CharField(choices=CLASS_TYPES)
id = models.IntegerField()
#field to identify FooBar
then you can get the object back using
object = FooBar.CLASS_TYPES[instance.type].objects.get(id=instance.id)
where instance is the FooBar instance

Returning extended fields in JSON

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?