Here is the model
class Student(models.Model):
"""Student info"""
id = models.CharField( max_length=7,primary_key=True)
name = models.CharField(_('name'),max_length=8, default=""); # help_text will locate after the field
address = models.CharField(_('address'),max_length=30,blank=True,default="") #blank true means the
GENDER_CHOICES = [("M", _("male")),("F",_("female"))]
student_number = models.CharField(max_length=10,blank=True)
gender = models.CharField(_("gender"),max_length=6, choices = GENDER_CHOICES, default="M");
I user shell to create two users as below:
But the queryset number didn't increase although I created two users.
#I hate Django. Q = Q
You are using a custom id field as model id and you put it as Char, so you should add this id also when you want to save an object
But it is not a good idea, if you want to use custom id use it in this way
id = models.AutoField(primary_key=True)
Related
currently I have terms on my applications and one user can have a lot of terms registered, and my current model is like this
class Term(models.Model):
id = models.UUIDField("id", default=uuid.uuid4, editable=False, primary_key=True)
user_id = models.PositiveIntegerField("user id", default=None)
name = models.CharField()
sometimes I need to do a query to get all the users who have terms registered, so I do the following query:
Term.objects.filter(active=True)
.order_by("user_id")
.values("user_id")
.distinct()
and this is enough to solve my problems, but now I'll change my model and it will look like this:
class Term(models.Model):
id = models.UUIDField("id", default=uuid.uuid4, editable=False, primary_key=True)
user_id = models.PositiveIntegerField("user id", default=None)
name = models.CharField()
shared_with = ArrayField(models.PositiveIntegerField("id do usuario"), blank=True) # New
How you can see, I've added a new field named shared_with, that basically is a array of user ids which I want to share terms, So now I need to make a query who will return all ids who can have terms registered (shared_with included). So if i register a Term with user_id = 1 and shared_with = [2,3], my query need to return [1,2,3].
I've solved this problem today with the following code, but I think I can do this just using django ORM and one query:
users = set()
for user in (
Term.objects.filter(active=True)
.order_by("user_id")
.values("user_id")
.distinct()
):
users.add(user["user_id"])
for user in (
Term.objects.filter(active=True)
.order_by("user_id")
.values("shared_with")
):
for user_id in user["shared_with"]:
users.add(user_id)
print(users) # {1,2,3}
If someone knows how to do it and can share the knowledge, I will be grateful.
I don't recommend using the PositiveIntegerField and ArrayField as relations between tables, you can use ForeignKey and ManyToManyField instead, in your case what I understand is a user can have many Terms and a Term can be shared among many users, so the perfect solution is to add ManyToManyField in your User model
class User(AbstarctUser):
... (your fields)
terms = models.ManyToManyField(Term, related_name="users")
and Term model will be like:
class Term(models.Model):
id = models.UUIDField("id", default=uuid.uuid4, editable=False, primary_key=True)
name = models.CharField(max_length=200)
active = models.BooleanField(default=True)
... (other fields)
in that case, if you want to extract user ids with active terms, you can get it as following :
users = User.objects.filter(terms__active=True).distinct().values_list("id", flat=True)
I am struggling to understand django models relationship.
I have this arborescence:
A train have cars, and those cars are divided into parts. Then those parts all contains different references.
Like, for exemple, all the trains have the 6 cars, and the cars 6 parts. Each part have x reference to be associated.
I would like to use all of them in a template later on, where the user can select the train, the car and the part he worked on, then generate a table from his selections with only the references associated to the parts he selected.
It should update the train and the car (I'm trying to update a stock of elements for a company)
I dont really understand which model field give to each of them. After checking the doc, Ive done something like this but i am not convinced:
class Train(Car):
train = models.CharField(max_length=200)
id = models.CharField(primary_key='True', max_length=100)
selected = models.BooleanField()
class Meta:
abstract = True
class Car(Part):
car = models.CharField(max_length=200)
id = models.CharField(primary_key='True', max_length=100)
selected = models.BooleanField()
class Meta:
abstract = True
class Part(Reference):
part = models.CharField(max_length=200)
id = models.CharField(primary_key='True', max_length=100)
selected = models.BooleanField()
class Meta:
abstract = True
class Reference(models.Model):
reference = models.CharField(max_length=200)
id = models.CharField(primary_key='True', max_length=100)
selected = models.BooleanField()
def __str__(self):
return self.reference
Can someone please help me understand this so I can do well ? Thanks!!
1-)if you add abstract = True in your Model Meta class, your class doesn't created on database as a table. If you store data for any class, you mustn't define abstract = True.
2-)For relations, you can use models.ForeignKey . If you add a class into brackets of another class, it names: inheritance.(You can think like parent-child relation). In database management, we can use foreignkey for one-to-many relationship.
3-)In Django ORM, id field automatically generated. So you don't need to define id field.
If I understand correctly, also you want to store parts of user's selected.
So, your model can be like that:
class Train(models.Model):
name = models.CharField(max_length=200) # I think you want to save name of train
class Car(models.Model):
train = models.ForeignKey(Train,on_delete=models.Cascade)
name = models.CharField(max_length=200)
class Part(models.Model):
car = models.ForeignKey(Car,on_delete=models.Cascade)
name = models.CharField(max_length=200)
class Reference(models.Model):
part = models.ForeignKey(Part,on_delete=models.Cascade)
name = models.CharField(max_length=200)
def __str__(self):
return self.reference
#addtional table for storing user's references
class UserReference(models.Model):
user = models.ForeignKey(User,on_delete=models.Cascade)
reference = models.ForeignKey(Reference,on_delete=models.Cascade)
name = models.CharField(max_length=200)
With this definitions, you can store user's definition on UserReference table. And with Django Orm, you can access train object from UserReferenceObject.
#user_reference: UserReference object like that result of UserReference.objects.first()
user_reference.reference.part.car.train.name
The goal of this project is to create an API that refreshes hourly with the most up to date betting odds for a list of games that I'll be scraping hourly from the internet. The goal structure for the JSON returned will be each game as the parent object and the nested children will be the top 1 record for each of linesmakers being scraped by updated date. My understanding is that the best way to accomplish this is to modify the to_representation function within the ListSerializer to return the appropriate queryset.
Because I need the game_id of the parent element to grab the children of the appropriate game, I've attempted to pull the game_id out of the data that gets passed. The issue is that this line looks to be populated correctly when I see what it contains through an exception, but when I let the full code run, I get a list index is out of range exception.
For ex.
class OddsMakerListSerializer(serializers.ListSerializer):
def to_representation(self, data):
game = data.all()[0].game_id
#if I put this here it evaluates to 1 which should run the raw sql below correctly
raise Exception(game)
data = OddsMaker.objects.filter(odds_id__in = RawSQL(''' SELECT o.odds_id
FROM gamesbackend_oddsmaker o
INNER JOIN (
SELECT game_id
, oddsmaker
, max(updated_datetime) as last_updated
FROM gamesbackend_oddsmaker
WHERE game_id = %s
GROUP BY game_id
, oddsmaker
) l on o.game_id = l.game_id
and o.oddsmaker = l.oddsmaker
and o.updated_datetime = l.last_updated
''', [game]))
#if I put this here the data appears to be populated correctly and contain the right data
raise Exception(data)
data = [game for game in data]
return data
Now, if I remove these raise Exceptions, I get the list index is out of range. My initial thought was that there's something else that depends on "data" being returned as a list, so I created the list comprehension snippet, but that doesn't resolve the issue.
So, my question is 1) Is there an easier way to accomplish what I'm going for? I'm not using a postgres backend so distinct on isn't available to me. and 2) If not, its not clear to me what instance is that's being passed in or what is expected to be returned. I've consulted the documentation and it looks as though it expects a dictionary and that might be part of the issue, but again the error message references a list. https://www.django-rest-framework.org/api-guide/serializers/#overriding-serialization-and-deserialization-behavior
I appreciate any help in understanding what is going on here in advance.
Edit:
The rest of the serializers:
class OddsMakerSerializer(serializers.ModelSerializer):
class Meta:
list_serializer_class = OddsMakerListSerializer
model = OddsMaker
fields = ('odds_id','game_id','oddsmaker','home_ml',
'away_ml','home_spread','home_spread_odds',
'away_spread_odds','total','total_over_odds',
'total_under_odds','updated_datetime')
class GameSerializer(serializers.ModelSerializer):
oddsmaker_set = OddsMakerSerializer(many=True, read_only=True)
class Meta:
model = Game
fields = ('game_id','date','sport', 'home_team',
'away_team','home_score', 'away_score',
'home_win','away_win', 'game_completed',
'oddsmaker_set')
models.py:
class Game(models.Model):
game_id = models.AutoField(primary_key=True)
date = models.DateTimeField(null=True)
sport=models.CharField(max_length=256, null=True)
home_team = models.CharField(max_length=256, null=True)
away_team = models.CharField(max_length=256, null=True)
home_score = models.IntegerField(default=0, null=True)
away_score = models.IntegerField(default=0, null=True)
home_win = models.BooleanField(default=0, null=True)
away_win = models.BooleanField(default=0, null=True)
game_completed = models.BooleanField(default=0, null=True)
class OddsMaker(models.Model):
odds_id = models.AutoField(primary_key=True)
game = models.ForeignKey('Game', on_delete = models.CASCADE)
oddsmaker = models.CharField(max_length=256)
home_ml = models.IntegerField(default=999999)
away_ml = models.IntegerField(default=999999)
home_spread = models.FloatField(default=999)
home_spread_odds = models.IntegerField(default=9999)
away_spread_odds = models.IntegerField(default=9999)
total = models.FloatField(default=999)
total_over_odds = models.IntegerField(default=999)
total_under_odds = models.IntegerField(default=999)
updated_datetime = models.DateTimeField(auto_now=True)
views.py:
class GameView(viewsets.ModelViewSet):
queryset = Game.objects.all()
serializer_class = GameSerializer
Thanks
To answer the question in the title:
The instance being passed to the Serializer.to_representation() is the instance you pass when initializing the serializer
queryset = MyModel.objects.all()
Serializer(queryset, many=True)
instance = MyModel.objects.all().first()
Serializer(data)
Usually you don't have to inherit from ListSerializer per se. You can inherit from BaseSerializer and whenever you pass many=True during initialization, it will automatically 'becomeaListSerializer`. You can see this in action here
To answer your problem
from django.db.models import Max
class OddsMakerListSerializer(serializers.ListSerializer):
def to_representation(self, data): # data passed is a queryset of oddsmaker
# Do your filtering here
latest_date = data.aggregate(
latest_date=Max('updated_datetime')
).get('latest_date').date()
latest_records = data.filter(
updated_date_time__year=latest_date.year,
updated_date_time__month=latest_date.month,
updated_date_time__day=latest_date.day
)
return super().to_representation(latest_records)
In django admin i had one model named 'student', here it has three fields, NAME, ROLL NO. & SUBJECT.
in models.py:
from django.db import models
class Student(models.Model):
Name = models.CharField(max_length=255, blank = False)
Roll_No = models.CharField(max_length=10, blank = False)
Subject = models.CharField(max_length=20, blank = False)
def __str__(self):
return self.Name
now i want this SUBJECT field to be Dynamic, like there will be "+" sign besides the SUBJECT field, by clicking that one more SUBJECT field will be added right after it and so on, but maximum 10 SUBJECT fields can be added like that.
You can update the existing value when doing the subject addition from views.
Like for example in views:
student = Student.objects.get(id=1)
student.Subject += "New_Subject_Name"
student.save() # this will update only
Add other conditions/check for the existing subject and check for 10 subjects accordingly.
the classes:
class User(flask_db.Model, UserMixin):
id = PrimaryKeyField()
social_id = CharField(null=False, unique=True)
nickname = CharField(null=False)
email = CharField(null=True)
class Feed(flask_db.Model):
id = PrimaryKeyField()
user = ForeignKeyField(User, related_name='feeds')
title = CharField()
url = CharField()
description = CharField()
If I do something like:
newfeed = Feed.create(..)
What should I put in the type id and in the type user ?
How should I get all the feeds of a User ?
With something like this ?
feedsofuserTom = Feed.select().where(Feed.user == userTom)
I don't understand the ForeignKeyField() function, I read the documentation but the examples didn't work for me. http://docs.peewee-orm.com/en/latest/peewee/models.html
ForeignKey is a relation between models.
ForeignKey is ManyToOne relation.
So for your Feed you can relate as many Users as you want.
So in your example firstly you have to create User instanse. And then add it while creating Feed.
first_user = User.create(social_id=1, nickname=name, email="email")
newfeed = Feed.create(user=first_user, title="cool feed", url="url.com", description="description")
As far as i remember you don't have to add PrimaryKeyField(). This field will be added automatically by database.