We Keep Coding

How to compare two serializer field and show whichever is higher in django rest

I have product serializer which return category_offer_price & product_offer_price,
before getting this response I want to compare both price and only return whichever is highest price.
#Serilaizer.py
class ProductSerializer(ModelSerializer):
category = CategorySerializer()
product_offer_price = SerializerMethodField()
category_offer_price = SerializerMethodField()
class Meta:
model = Products
fields = [
"id",
"product_name",
"slug",
"category",
"description",
"category_offer_price",
"product_offer_price",
"base_price",
"stock",
"is_available",
"created_date",
"images",
"images_two",
"images_three",
]
def get_product_offer_price(self, obj):
try:
product_offer = ProductOffer.objects.get(product=obj)
if product_offer.is_active:
offer_price = product_offer.product_offer_price()
return offer_price
except Exception:
pass
return None
def get_category_offer_price(self, obj):
try:
category_offer = CategoryOffer.objects.get(category=obj.category)
if category_offer.is_active:
offer_price = category_offer.category_offer_price(obj)
return offer_price
except Exception:
pass
return None
#Models.py
class Products(models.Model):
category = models.ForeignKey(Category, on_delete=models.CASCADE)
product_name = models.CharField(max_length=50, unique=True)
slug = models.SlugField(max_length=100, unique=True)
description = models.TextField(max_length=500)
base_price = models.IntegerField()
images = models.ImageField(upload_to="photos/products")
images_two = models.ImageField(upload_to="photos/products")
images_three = models.ImageField(upload_to="photos/products")
stock = models.IntegerField()
is_available = models.BooleanField(default=True)
created_date = models.DateTimeField(auto_now_add=True)
modified_date = models.DateTimeField(auto_now=True)
class Meta:
verbose_name_plural = "Products"
def __str__(self):
return self.product_name
I'd like to know is it possible to compare serializer fields in a serializer class?

You can move into one method, to validate your field. Also, substitute your try:except with get-object-or-404 method and your serializer fields with all value since you are using everything, to have a much cleaner code.
from django.shortcuts import get_object_or_404
class ProductSerializer(ModelSerializer):
category = CategorySerializer()
price = SerializerMethodField()
class Meta:
model = Products
fields = '__all__'
def get_price(self, obj):
product_offer = get_object_or_404(ProductOffer, product=obj)
category_offer = get_object_or_404(CategoryOffer, category=obj.category)
if product_offer.is_active and category_offer.is_active:
if product_offer.product_offer_price() > category_offer.category_offer_price(obj):
return product_offer.product_offer_price()
else:
return category_offer.category_offer_price(obj)
elif product_offer.is_active and not category_offer.is_active:
return product_offer.product_offer_price()
elif category_offer.is_active and not product_offer.is_active:
return category_offer.category_offer_price(obj)
EDIT: As you can see I used the classic if/else in this solution, although since Python 3.10 you can use the Match case statement to substitute these conditions chain.
In case of objects do not exist:
class ProductSerializer(ModelSerializer):
category = CategorySerializer()
price = SerializerMethodField()
class Meta:
model = Products
fields = '__all__'
def get_price(self, obj):
try:
product_offer = ProductOffer.objects.filter(product=obj).first()
category_offer = CategoryOffer.objects.filter(category=obj.category).first()
if not product_offer and not category_offer:
return obj.base_price
elif not category_offer:
return product_offer.product_offer_price()
elif not product_offer:
return category_offer.category_offer_price(obj)
elif category_offer and product_offer:
if category_offer.is_active and not product_offer.is_active:
return category_offer.category_offer_price(obj)
elif product_offer.is_active and not category_offer.is_active:
return product_offer.product_offer_price()
elif category_offer.is_active and product_offer.is_active:
if category_offer.category_offer_price(obj) > product_offer.product_offer_price():
return category_offer.category_offer_price(obj)
else:
return product_offer.product_offer_price()
except:
return obj.base_price
Although, to be honest, if there could be no objects then the is_active field is redundant.

You can override to_representation()
Example:
class ProductSerializer(ModelSerializer):
category = CategorySerializer()
product_offer_price = SerializerMethodField()
category_offer_price = SerializerMethodField()
...
...
def to_representation(self, instance):
data = super().to_representation(instance)
# access required fields like this
product_offer_price = data['product_offer_price']
category_offer_price = data['category_offer_price']
# do calculations here and returning the desired field as `calculated_price`
if category_offer_price > product_offer_price:
data['calculated_price'] = category_offer_price
else:
data['calculated_price'] = product_offer_price
return data

Not sure it s what you want but you could use a field of type SerializerMethodField which allow you to add a computed field that you could call category_offer_higher_price. Its value is computed by a function that return the highest one. See following link : https://www.django-rest-framework.org/api-guide/fields/#serializermethodfield

DRF Create new object and link to (but not create) it's related items (nested serializer)?

I'm trying to link multiple items (subdomains) to an item being created (evidence).
My form submits okay - but I'm trying to figure out the 'best' way to go about this.
According to the docs I have to override the create method - but their example shows them 'creating' the related objects.
I don't want to do that. I want to just just add those related items to the piece of evidence I am creating (to create the relationship)
Here are my serializers:
class SubdomainSerializer(serializers.ModelSerializer):
class Meta:
model = Subdomain
fields = [
"id",
"domain",
"short_description",
"long_description",
"character_code",
]
class EvidenceSerializer(serializers.ModelSerializer):
"""
"""
created_by = serializers.HiddenField(
default=serializers.CurrentUserDefault()
)
updated_by = serializers.HiddenField(
default=serializers.CurrentUserDefault()
)
absolute_url = serializers.SerializerMethodField()
created_by_name = serializers.SerializerMethodField()
updated_by_name = serializers.SerializerMethodField()
subdomains = SubdomainSerializer(many=True)
class Meta:
model = Evidence
fields = "__all__"
extra_kwargs = {
"subdomains": {
"error_messages": {
"null": "This field is required.",
"blank": "This field is required.",
}
},
}
def get_absolute_url(self, obj):
return obj.get_absolute_url()
def get_created_by_name(self, obj):
return obj.created_by.full_name
def get_updated_by_name(self, obj):
return obj.updated_by.full_name
def create(self, validated_data):
subdomains_data = validated_data.pop("subdomains")
evidence = Evidence.objects.create(**validated_data)
for subdomain in subdomains_data:
# This is where I want to add the subdomains to the evidence - not create ones - how best to accomplish that?
Subdomain.objects.create(**subdomain)
return evidence
def update(self, instance, validated_data):
# Add the requestor as the updater in a PATCH request
request = self.context["request"]
validated_data["updated_by"] = request.user
return super().update(instance, validated_data)
Is there a better way to setup my serializers? Should I be doing something different to make this more achievable?
Edited to add my models:
class Subdomain(CreateUpdateMixin):
"""
"""
domain = models.ForeignKey(Domain, on_delete=models.PROTECT)
short_description = models.CharField(max_length=100)
long_description = models.CharField(max_length=250)
character_code = models.CharField(max_length=5)
proficiency_levels = models.ManyToManyField(SubdomainProficiencyLevel)
class Meta:
verbose_name = "Subdomain"
verbose_name_plural = "Subdomains"
def __str__(self):
"""Unicode representation of Subdomain."""
return f"{self.character_code}"
class Evidence(CreateUpdateMixin, CreateUpdateUserMixin, SoftDeletionModel):
"""
"""
subdomains = models.ManyToManyField(Subdomain, related_name="evidences")
evaluation = models.ForeignKey(
Evaluation, related_name="evidences", on_delete=models.PROTECT
)
published = models.BooleanField(default=False)
comments = models.CharField(max_length=500)
class Meta:
ordering = ["-created_at"]
verbose_name = "Evidence"
verbose_name_plural = "Evidence"
def __str__(self):
"""Unicode representation of Evidence."""
return f"{self.subdomain} : {self.comments}"
def get_absolute_url(self):
"""Return absolute url for Evidence."""
return reverse("evidence-detail", args=[str(self.id)])

Here you want to set the subdomain ForeignKey to the new created evidence.
For that, you just have to retrieve the subdomain and update his evidence field like this :
def create(self, validated_data):
subdomains_data = validated_data.pop("subdomains")
evidence = Evidence.objects.create(**validated_data)
for subdomain in subdomains_data:
# Retrieve the subdomain and update the evidence attribute
sub_id = subdomain['id']
sub = Subdomain.objects.get(id=sub_id)
sub.evidence = evidence
sub.save()
return evidence
NB : I use the default inverse ForeignKey relationship : sub.evidence

How to validate a django modelform if the form has some other fields

I have made a Django model form but the problem is in my logic I am using something else and now I want to figure out a way to validate it by either defining a Meta class and choosing the fields that I want to display to the user but of course this won't validate the form.
Now I want to know if there is a way to validate the form without touching the models and pass the data required for the logic and after take care of the information needed for the data of the model to be saved.
Here is the models:
from django.db import models
from django.db import models
from django.contrib.auth.models import User
# Create your models here.
class RoomCategory(models.Model):
name = models.CharField(max_length=59)
price = models.IntegerField()
beds = models.PositiveIntegerField()
capacity = models.PositiveIntegerField()
size = models.CharField(max_length=59)
def __str__(self):
return self.name
class Room(models.Model):
room_number = models.CharField(max_length=60)
room_category = models.ForeignKey(RoomCategory, on_delete=models.CASCADE)
def __str__(self):
return f"The room {self.room_number} {self.room_category} has a maximum of {self.room_category.capacity} person and cost {self.room_category.price}/night "
class Booking(models.Model):
customer = models.ForeignKey(User, on_delete=models.CASCADE)
room = models.ForeignKey(RoomCategory, on_delete=models.CASCADE)
check_in = models.DateField()
check_out = models.DateField()
adults = models.PositiveSmallIntegerField()
children = models.PositiveSmallIntegerField()
def __str__(self):
return f"{self.customer} has booked for {self.room} from {self.check_in} to {self.check_out}"
Here is the form:
class BookingForm(forms.ModelForm):
class Meta:
model = Booking
fields = ['room', 'check_in', 'check_out', 'adults', 'children']
here is the views.py
data = form.cleaned_data
roomlist = Room.objects.filter(room_category__name=data['room'])
available_rooms = []
for room in roomlist:
if data['adults'] + data['children'] > room.room_category.capacity:
return HttpResponse(f'Sorry !! But this category of room cannot handle more than {room.room_category.capacity}')
else:
if check_availability(room.room_category.name, data['check_in'], data['check_out'], data['adults'], data['children']):
available_rooms.append(room)
if len(available_rooms) > 0:
room = available_rooms[0]
new_booking = Booking.objects.create(
customer=self.request.user,
room=room,
check_in=data['check_in'],
check_out=data['check_out'],
adults=data['adults'],
children=data['children']
)
new_booking.save()
return HttpResponse(new_booking)
else:
return HttpResponse('All the rooms of this type are not available')
It is not printing the data means that the form is not valid and it fall down to the else statement.

You can validate any field in the form by writing a method in this way : def clean_(field_name) i.e def clean_room(self) read more:
https://docs.djangoproject.com/en/3.1/ref/forms/validation/#cleaning-a-specific-field-attribute

Django serializer, nested relation and get_or_create

I've been bugging on this issue for some time now. I have two models : Acquisitions and RawDatas.
Each RawData have one Acquisition, but many RawDatas can have the same Acquisition.
I want to create or get the instance of Acquisition automatically when I create my RawDatas. And I want to be able to have all informations using the serializer.
class Acquisitions(models.Model):
class Meta:
unique_together = (('implant', 'beg_acq', 'duration_acq'),)
id = models.AutoField(primary_key=True)
implant = models.ForeignKey("Patients", on_delete=models.CASCADE)
beg_acq = models.DateTimeField("Beggining date of the acquisition")
duration_acq = models.DurationField("Duration of the acquisition")
class RawDatas(models.Model):
class Meta:
unique_together = (('acq', 'data_type'),)
id = models.AutoField(primary_key=True)
acq = models.ForeignKey("Acquisitions", on_delete=models.CASCADE)
data_type = models.CharField(max_length=3)
sampling_freq = models.PositiveIntegerField("Sampling frequency")
bin_file = models.FileField(db_index=True, upload_to='media')
And my serializers are these :
class AcquisitionSerializer(serializers.ModelSerializer):
class Meta:
model = Acquisitions
fields = ('id', 'implant', 'beg_acq', 'duration_acq')
class RawDatasSerializer(serializers.ModelSerializer):
acq = AcquisitionSerializer()
class Meta:
model = RawDatas
fields = ('id', 'data_type', 'sampling_freq', 'bin_file', 'acq')
def create(self, validated_data):
acq_data = validated_data.pop('acq')
acq = Acquisitions.objects.get_or_create(**acq_data)
RawDatas.objects.create(acq=acq[0], **validated_data)
return rawdatas
My problem is that, using this, if my instance of Acquisitions already exists, I get a non_field_errors or another constraint validation error.
I would like to know what is the correct way to handle this please ?
So I can automatically create this using the nested serializer, and when I only want to have informations (such as a GET request), I can have all the field I need (every field of the two models).
Thanks in advance for your help !

Try this:
class AcquisitionSerializer(serializers.ModelSerializer):
class Meta:
model = Acquisitions
fields = ('id', 'implant', 'beg_acq', 'duration_acq')
class RawDatasSerializer(serializers.ModelSerializer):
class Meta:
model = RawDatas
fields = ('id', 'data_type', 'sampling_freq', 'bin_file', 'acq')
def create(self, validated_data):
acq_data = validated_data.pop('acq')
acq = Acquisitions.objects.filter(id=acq_data.get('id')).first()
if not acq:
acq = AcquisitionSerializer.create(AcquisitionSerializer(), **acq_data)
rawdata = RawDatas.objects.create(acq=acq, **validated_data)
return rawdata

How do I filter values in a Django form using ModelForm?

I am trying to use the ModelForm to add my data. It is working well, except that the ForeignKey dropdown list is showing all values and I only want it to display the values that a pertinent for the logged in user.
Here is my model for ExcludedDate, the record I want to add:
class ExcludedDate(models.Model):
date = models.DateTimeField()
reason = models.CharField(max_length=50)
user = models.ForeignKey(User)
category = models.ForeignKey(Category)
recurring = models.ForeignKey(RecurringExclusion)
def __unicode__(self):
return self.reason
Here is the model for the category, which is the table containing the relationship that I'd like to limit by user:
class Category(models.Model):
name = models.CharField(max_length=50)
user = models.ForeignKey(User, unique=False)
def __unicode__(self):
return self.name
And finally, the form code:
class ExcludedDateForm(ModelForm):
class Meta:
model = models.ExcludedDate
exclude = ('user', 'recurring',)
How do I get the form to display only the subset of categories where category.user equals the logged in user?

You can customize your form in init
class ExcludedDateForm(ModelForm):
class Meta:
model = models.ExcludedDate
exclude = ('user', 'recurring',)
def __init__(self, user=None, **kwargs):
super(ExcludedDateForm, self).__init__(**kwargs)
if user:
self.fields['category'].queryset = models.Category.objects.filter(user=user)
And in views, when constructing your form, besides the standard form params, you'll specify also the current user:
form = ExcludedDateForm(user=request.user)

Here example:
models.py
class someData(models.Model):
name = models.CharField(max_length=100,verbose_name="some value")
class testKey(models.Model):
name = models.CharField(max_length=100,verbose_name="some value")
tst = models.ForeignKey(someData)
class testForm(forms.ModelForm):
class Meta:
model = testKey
views.py
...
....
....
mform = testForm()
mform.fields["tst"] = models.forms.ModelMultipleChoiceField(queryset=someData.objects.filter(name__icontains="1"))
...
...
Or u can try something like this:
class testForm(forms.ModelForm):
class Meta:
model = testKey
def __init__(self,*args,**kwargs):
super (testForm,self ).__init__(*args,**kwargs)
self.fields['tst'].queryset = someData.objects.filter(name__icontains="1")

I know this is old; but its one of the first Google search results so I thought I would add how I found to do it.
class CustomModelFilter(forms.ModelChoiceField):
def label_from_instance(self, obj):
return "%s %s" % (obj.column1, obj.column2)
class CustomForm(ModelForm):
model_to_filter = CustomModelFilter(queryset=CustomModel.objects.filter(active=1))
class Meta:
model = CustomModel
fields = ['model_to_filter', 'field1', 'field2']
Where 'model_to_filter' is a ForiegnKey of the "CustomModel" model
Why I like this method:
in the "CustomModelFilter" you can also change the default way that the Model object is displayed in the ChoiceField that is created, as I've done above.

is the best answer:
BookDemoForm.base_fields['location'] = forms.ModelChoiceField(widget=forms.Select(attrs={'class': 'form-control select2'}),queryset=Location.objects.filter(location_for__fuel=True))