I've the following model:
class Quiz(models.Model):
name = models.CharField(max_length=255)
month = models.DateField()
class Question(models.Model):
title = models.CharField(max_lenght=255)
category = models.CharField(max_length=255)
status = models.CharField(max_length=255, status=(('Pending', 'Pending'), ('Approved', 'Approved'))
class Contest(models.Model):
quiz = models.ForeignKey(Quiz, on_delete=models.CASCADE)
questions = models.ManyToManyField(Question, related_name='contest_questions')
Now I want to get list of quizes with all questions whose status=Pending?
Any help would be much appreciated!
Another approach is query directly from the M2M table using values_list():
quiz_ids = list(Contest.objects.filter(questions__status='Pending').values_list('quiz__id', flat=True))
quiz_query = Quiz.objects.filter(id__in=quiz_ids)
Related
I have 3 django tables connected like this:
Is there anyway to make a query for table Table that will get id_equip from table equip?
models.py
class Vendor(models.Model):
vendor_name = models.CharField(max_length=50)
def __str__(self):
return self.vendor_name
class Equipment(models.Model):
equipment_name = models.CharField(max_length=50)
id_vendor = models.ForeignKey(Vendor, on_delete=models.CASCADE, default=None)
def __str__(self):
return self.equipment_name
class Table(models.Model):
table_name = models.CharField(max_length=100)
id_vend = models.ForeignKey(Vendor, on_delete=models.CASCADE, default=None)
id_equip = models.ManyToManyField(Equipment)
This part of the django docs is relevant and helpful, I definitely recommend your review at least that section and ideally the whole page.
Your models are already denormalized as evidenced by Table.id_equip which relates to Equipment so you could do:
table = Table.objects.get(SOME_FILTER)
equipment_ids = list(table.id_equip.all().values_list('id', flat=True))
If you wanted to go through the vendor I'd suggest:
table = Table.objects.get(SOME_FILTER)
equipment_ids = list(Equipment.objects.filter(vendor_set__table_set=table).values_list('id', flat=True))
I would recommend that you don't name your relationship fields with id_. With an ORM, these fields should represent the instances of the Model they are mapping to. For example:
class Table(models.Model):
name = models.CharField(max_length=100)
vendor = models.ForeignKey(Vendor, on_delete=models.CASCADE, default=None)
equipment = models.ManyToManyField(Equipment)
If you're trying to create the model on top of an existing table, you can make use of the db_column parameter when defining the field.
vendor = models.ForeignKey(Vendor, on_delete=models.CASCADE, default=None, db_column="id_vend")
I have two models:
Lot:
class Lot(models.Model):
name = models.CharField(max_length=150, db_index=True, unique=True)
step = models.DecimalField(max_digits=2, decimal_places=2)
and Bid:
class Bid(models.Model):
auction = models.ForeignKey('Lot', on_delete=models.CASCADE)
user_id = models.ForeignKey(User, on_delete=models.CASCADE, to_field='username')
value = models.DecimalField(max_digits=5, decimal_places=2)
Every instance of Lot can have a few Bids, however any instance of Bid is only related to a particular Lot.
I have a working annotation for Lot that gives me the max_bid and next_bid values:
self.auc_set = Lot.objects.annotate(max_bid=Max('bid__value'), next_bid=(Max('bid__value') + F('step')))
And what i can't achieve is getting 3 annotated fields: max_bid, next_bid and last_bidder.
Something like:
self.auc_set = Lot.objects.annotate(max_bid=Max('bid__value'), next_bid=(Max('bid__value') + F('step')), last_bidder=F(bid_set).get('auction_id'= F('id'), 'value'=max_bid)['user_id'])
but working.
Update:
The problem would be solved if i knew how to pass the 'id' from Lot.objects.annotate to the Bid.objects.get part:
auc_set = Lot.objects.annotate(last_bidder=Bid.objects.get(auction_id__exact='need_to_put_something_here', value=Max('value').user_id)
Preliminary note: this is a rather newbie question, though I have not found a sufficient answer on StackOverflow; many similar questions, but not this one. So I am asking a new question.
The problem: I'm having difficulty creating records where one field is a foreign key to an existing record, and I do not know what I'm doing wrong in my code.
In my app there are two models in question, a one-to-many relationship between Company and BalanceSheet:
models:
class Company(models.Model):
cik = models.IntegerField(default=0, unique=True)
symbol = models.CharField(max_length=4, unique=True)
name = models.CharField(max_length=255, unique=True)
def __str__(self):
return self.symbol
class BalanceSheet(models.Model):
company = models.ForeignKey(Company,
null=True,
on_delete=models.CASCADE,
related_name='balance_sheets',)
date = models.DateField()
profit = models.BigIntegerField()
loss = models.BigIntegerField()
class Meta:
unique_together = (('company', 'date'),)
def __str__(self):
return '%s - %s' % (self.company, self.date)
serializers:
class BalanceSheetSerializer(serializers.ModelSerializer):
company = serializers.StringRelatedField()
class Meta:
model = BalanceSheet
fields = ('company','date','profit','loss')
class CompanySerializer(serializers.ModelSerializer):
class Meta:
model = Company
fields = ('cik', 'symbol', 'name')
Views:
class BalanceSheetCreate(generics.CreateAPIView):
model = BalanceSheet
queryset = BalanceSheet.objects.all()
serializer_class = BalanceSheetSerializer
urls include:
url(r'^(?P<symbol>[A-Z]{1,4})/create-balance-sheet/$', views.BalanceSheetCreate.as_view(),
name='create_balance_sheet'),
To this point, I have zero problem reading data. However, when trying to create records, I get errors I don't understand:
curl http://localhost:8000/financials/AAPL/create-balance-sheet/ -X POST -d "company=AAPL&date=1968-04-17&profit=1&loss=1"
IntegrityError at /financials/AAPL/create-balance-sheet/
null value in column "company_id" violates not-null constraint
Dropping the company data from that curl command results in the same error.
How do I get around this error? I thought I was telling the api what company I'm interested in, both explicitly in the url and in the post data.
Using python3.6, django 1.11, and djangorestframework 3.7.7
You get the IntegrityError because your code will try to create a new BalanceSheet without a company. That's because StringRelatedField is read-only (see docs) and therefore it's not parsed when BalanceSheetSerializer is used in write mode.
SlugRelatedField is what you need here:
class BalanceSheetSerializer(serializers.ModelSerializer):
company = serializers.SlugRelatedField(slug_field='symbol')
class Meta:
model = BalanceSheet
fields = ('company','date','profit','loss')
To answer my own question, here's what I wound up with. Thanks again go to dukebody.
models:
class Company(models.Model):
cik = models.IntegerField(default=0)
symbol = models.CharField(max_length=4)
name = models.CharField(max_length=255)
def __str__(self):
return self.symbol
class BalanceSheet(models.Model):
company = models.ForeignKey(Company,
null=True,
on_delete=models.CASCADE,
related_name='balance_sheets',)
date = models.DateField()
profit = models.BigIntegerField()
loss = models.BigIntegerField()
class Meta:
unique_together = (('company', 'date'),)
def __str__(self):
return '%s - %s' % (self.company, self.date)
serializers:
class CompanySerializer(serializers.ModelSerializer):
class Meta:
model = Company
fields = ('cik', 'symbol', 'name')
class BalanceSheetSerializer(serializers.ModelSerializer):
company = CompanySerializer(many=False)
class Meta:
model = BalanceSheet
fields = ('company', 'date', 'profit', 'loss')
def create(self, validated_data):
company_data = validated_data['company']
company, created = Company.objects.get_or_create(**company_data)
validated_data['company'] = company
sheet = BalanceSheet.objects.create(**validated_data)
return sheet
I also had to include the full company data within my curl statement as a nested dict.
I'm having problems trying to use the queryset filter with my models.
It is a control for posts in groups.
This is my code:
class Post(models.Model):
title = models.CharField(max_length=120)
content = models.TextField()
class Group(models.Model):
title = models.CharField(max_length=200)
url = models.URLField(unique=True)
class Control(models.Model):
published = models.DateField(auto_now=False, auto_now_add=False)
group = models.ForeignKey(Group, on_delete=models.CASCADE)
post = models.ForeignKey(Post, on_delete=models.CASCADE)
I'm trying to get all posts from a group with the title "title":
queryset_list = Control.objects.filter(group__control="title")
My models might nit be right, I'm new to this.
Any help?
Maybe it typo error?
queryset_list = Control.objects.filter(group__title="title")
# ^^^^^^
posts_title = queryset_list.values('post__title')
First, you should add a ManyToManyField on Group (docs):
class Group(models.Model):
title = models.CharField(max_length=200)
url = models.URLField(unique=True)
posts = models.ManyToManyField('Post', through='Control')
The other two models remain the same, but now you can easily grab posts for a Group:
posts = Group.objects.get(title='some title').posts.all()
i am developing a rest API using django rest framework and i am stuck at a serializer the idea is to serialize a self recursive many to many model using a through table my code is:
model.py:
class Patient(models.Model):
class Meta:
db_table = 'patients'
id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False, unique=True)
id_card = models.CharField(max_length=45)
dob = models.DateField()
gender = EnumChoiceField(enum_class=Gender)
patientscol = models.CharField(max_length=45)
fk_user = models.ForeignKey(Users, related_name='user_patient', on_delete=models.CASCADE)
relative = models.ManyToManyField("self", through='PatientHasRelative')
class PatientHasRelative(models.Model):
class Meta:
db_table = 'patients_has_relatives'
fk_patient = models.ForeignKey(Patient, related_name='patient_has', on_delete=models.CASCADE)
fk_relative_patient = models.ForeignKey(Patient, related_name='patient_relative', on_delete=models.CASCADE)
relationship = EnumChoiceField(enum_class=Relationship)
my serializer.py is:
class PatientSerializer(serializers.ModelSerializer):
class Meta:
model = Patient
fields = ('__all__')
id = serializers.UUIDField(read_only=True)
id_card = serializers.CharField(required=True, max_length=45)
dob = serializers.DateField(required=True)
gender = EnumChoiceField(enum_class=Gender)
fk_user = serializers.PrimaryKeyRelatedField(required=True, queryset=Users.objects.all())
relative = PatientSerializer(read_only=True, required=True)#problem is here i cant use PatientSerializer here
class PatientHasRelativeSerializer(serializers.ModelSerializer):
class Meta:
model = PatientHasRelative
fields = ('__all__')
fk_patient = serializers.PrimaryKeyRelatedField(required=True, queryset=Patient.objects.all())
fk_relative_patient = serializers.PrimaryKeyRelatedField(required=True, queryset=Patient.objects.all())
relationship = EnumChoiceField(enum_class=Relationship)
a little help would be appreciated
To accomplish this you need to define related_name in the source model on the source field ie add
class Patient(models.Model):
relatives = models.ManyToManyField(
"self", through='PatientHasRelative', related_name='patients')
with this related_name you can easily access -- add/delete/set relatives/patients on either side of the relationships in the serializers
You can either do this using intermediary model
relative = Patient(**key_value_fields)
patient = Patient(**key_value_field)
PatientHasRelative.objects.create(
relative=relative, patient=patient, through_defaults=(relationship ='value',))
or you can do this
relative.patients.add(patient, through_defaults=relationship ='value')
or this
patient.relatives.add(relative, through_defaults=relationship ='value')
example retrieving
patient.relatives.all()