Hello to the stackoverflow team,
I have the following two django tables:
class StraightredFixture(models.Model):
fixtureid = models.IntegerField(primary_key=True)
soccerseason = models.IntegerField(db_column='soccerSeason') # Field name made lowercase.
hometeamid = models.IntegerField()
awayteamid = models.IntegerField()
fixturedate = models.DateTimeField()
fixturestatus = models.CharField(max_length=24)
fixturematchday = models.IntegerField()
hometeamscore = models.IntegerField()
awayteamscore = models.IntegerField()
class Meta:
managed = False
db_table = 'straightred_fixture'
class StraightredTeam(models.Model):
teamid = models.IntegerField(primary_key=True)
teamname = models.CharField(max_length=36)
teamcode = models.CharField(max_length=5)
teamshortname = models.CharField(max_length=24)
class Meta:
managed = False
db_table = 'straightred_team'
In the views.py I know I can put the following and it works perfectly:
def test(request):
fixture = StraightredFixture.objects.get(fixtureid=136697)
return render(request,'straightred/test.html',{'name':fixture.hometeamid})
As I mentioned above, this all works well but I am looking to return the teamname of the hometeamid which can be found in the StraightredTeam model.
After some looking around I have been nudged in the direction of "select_related" but I am unclear on how to implement it in my existing tables and also if it is the most efficient way for this type of query. It feels right.
Please note this code was created using "python manage.py inspectdb".
Any advice at this stage would be greatly appreciated. Many thanks, Alan.
See model relationships.
Django provides special model fields to manage table relationships.
The one suiting your needs is ForeignKey.
Instead of declaring:
hometeamid = models.IntegerField()
awayteamid = models.IntegerField()
which I guess is the result of python manage.py inspectdb, you would declare:
home_team = models.ForeignKey('<app_name>. StraightredTeam', db_column='hometeamid', related_name='home_fixtures')
away_team = models.ForeignKey('<app_name>. StraightredTeam', db_column='awayteamid', related_name='away_fixtures')
By doing this will, you tell the Django ORM to handle the relationship under the hood, which will allow you to do such things as:
fixture = StraightredFixture.objects.get(fixtureid=some_fixture_id)
fixture.home_team # Returns the associated StraightredTeam instance.
team = StraightredTeam.objects.get(team_id=some_team_id)
team.home_fixtures.all() # Return all at home fixtures for that team.
I am not sure if this makes sense for Managed=False, but I suppose the sane way of doing it in Django would be with
home_team = models.ForeignKey('StraightRedFixture', db_column='fixtureid'))
And then just using fixture.home_team instead of doing queries by hand.
Related
I'm new to Django
I'm currently using django 3.2.6. I want make multiple instances of route_stop model and store in SchoolRouteStop.route_graph model.I don't want use ForeignKey because i want to make somthing like like nested dict.
from django.db import models
class geo_fence(models.Model):
radius = models.FloatField()
class geo_location(models.Model):
latitude = models.FloatField()
longitude = models.FloatField()
class address(models.Model):
entity = models.fields.CharField(max_length=100)
apt_plot = models.fields.CharField(max_length=100)
street = models.fields.CharField(max_length=100)
city = models.fields.CharField(max_length=100)
state = models.fields.CharField(max_length=2) #state name in short code
zip_code = models.fields.IntegerField()
class route_stop(models.Model): # this for multiple bus stops
route_stop_id = models.fields.IntegerField()
school_id = models.fields.CharField(max_length=100)
route_number = models.fields.CharField(max_length=100)
school_route_stop_uuid = models.fields.CharField(max_length=100, primary_key=True)
registered_arrival_time = models.TimeField()
time_from_src = models.FloatField()
is_school = models.BooleanField(default=False)
geo_fence = models.ForeignKey(geo_fence, on_delete =models.CASCADE)
geo_location = models.ForeignKey(geo_location, on_delete = models.CASCADE)
address = models.ForeignKey(address, on_delete = models.CASCADE)
class SchoolRouteStop(models.Model):
school_id = models.CharField(max_length=100)
school_route_number = models.IntegerField()
route_type = models.CharField(max_length=2)
route_id = str(school_id)+'_'+str(school_route_number)+str(route_type)
route_graph= models.ForeignKey(route_stop,related_name='School', on_delete = models.CASCADE)
# Create your models here.
You have to use a ForeignKey here because you will lose all the Django ORM features and performances if you try to hack this.
Trying to use a JSONField or something else instead would also mean losing integrity constraints you would need to implement yourself, which you really want to avoid.
The way Django works is you implement your models to be stored efficiently in the database, then you use views & serializers to manipulate them.
Your models need to be refined, I really have a hard time understanding their real purpose because there are id fields everywhere (that should also probably be ForeignkeyField), and everything seems a little confusing.
For example, why is school_route_stop_uuid a CharField when UUIDField does exist?
Why is route_id not a property?
Also, make sure to follow the naming conventions in Python, it will make you code way cleaner. According to PEP 8 (https://www.python.org/dev/peps/pep-0008/#class-names):
Class names should normally use the CapWords convention.
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)
I have models defined like so:
class Games(models.Model):
title = models.CharField(max_length=50)
owned = models.BooleanField(default=False)
created = models.DateTimeField(auto_now_add=True)
class Votes(models.Model):
game = models.ForeignKey(Games)
created = models.DateTimeField(auto_now_add=True)
And i'm doing the following in my view:
wanted = Games.objects.filter(owned=0)
for game in wanted:
game.vote = Votes.objects.all().filter(game_id=game.id).count()
wanted = sorted(wanted, key=attrgetter('vote'), reverse=True)
It works fine but is there a more Django way of doing this?
from django.db.models import Count
Games.objects.filter(owned=0).annotate(vote=Count('votes')).order_by('-vote')
see Django aggregation for more information
i'm trying to 'join' this 4 models in a query. My starting point is a Team.id.
I am trying to get the SkillRecord into the result but i am completly lost.
class Team(models.Model):
user = models.ForeignKey(User)
id = models.IntegerField(primary_key=True, null=False, unique=True)
...
class Player(models.Model):
id = models.IntegerField(primary_key=True)
...
class Transfer(models.Model):
player = models.ForeignKey(Player)
seller = models.ForeignKey(Team, related_name='transfer_seller')
buyer = models.ForeignKey(Team, related_name='transfer_buyer')
date = models.DateTimeField()
...
class SkillRecord(models.Model):
player = models.ForeignKey(Player)
date = models.DateTimeField(default=datetime.datetime.now)
...
Here is my humble approach so far
def list_players(request, teamid):
team = get_object_or_404(Team, id=teamid)
players_transfers = Transfer.objects.filter(buyer=team).select_related('player')
I'm not really sure what would be my next step to get the SkillRecord model into the game.
I seem to lack the basic gist of those kind of problems so i will need a poke i guess.
Also, feel free to give me further ideas how to do this, i'm more or less sure i could also solve this whole Transfer thing using manytomanyfields or so.
Thanks a lot
To grab SkillRecord as well you need to add related_name:
class SkillRecord(models.Model):
player = models.ForeignKey(Player, related_name='skills')
date = models.DateTimeField(default=datetime.datetime.now)
then make the query:
qt = Transfer.objects.filter(...).select_related('player').prefetch_related('player__skills')
then retrieve them like so:
qt[0].player.skills.all()
Making some assumptions each Player has a Team so we can add.
class Player(models.Model):
team = models.ForeignKey(Team)
Then if you want the skillrecord start by there
SkillRecord.objects.filter(player__team=team)