I have three models:
Course
Assignment
Term
A course has a ManyToManyField which accesses Django's default User in a field called student, and a ForeignKey with term
An assignment has a ForeignKey with course
Here's the related models:
class Assignment(models.Model):
title = models.CharField(max_length=128, unique=True)
points = models.IntegerField(default=0, blank=True)
description = models.TextField(blank=True)
date_due = models.DateField(blank=True)
time_due = models.TimeField(blank=True)
course = models.ForeignKey(Course)
class Course(models.Model):
subject = models.CharField(max_length=3)
number = models.CharField(max_length=3)
section = models.CharField(max_length=3)
professor = models.ForeignKey("auth.User", limit_choices_to={'groups__name': "Faculty"}, related_name="faculty_profile")
term = models.ForeignKey(Term)
students = models.ManyToManyField("auth.User", limit_choices_to={'groups__name': "Student"}, related_name="student_profile")
When a user logs in to the page, I would like to show them something like this bootstrap collapse card where I can display each term and the corresponding classes with which the student is enrolled.
I am able to access all of the courses in which the student is enrolled, I'm just having difficulty with figuring out the query to select the terms. I've tried using 'select_related' with no luck although I may be using it incorrectly. So far I've got course_list = Course.objects.filter(students = request.user).select_related('term'). Is there a way to acquire all of the terms and their corresponding courses so that I can display them in the way I'd like? If not, should I be modeling my database in a different way?
https://docs.djangoproject.com/en/1.11/ref/models/querysets/#values
You could use values or values_list here to get the fields of the related model Term.
For example expanding on your current request:
To retrieve all the Terms' name and duration for the Courses in your queryset
Course.objects.filter(students = request.user).values('term__name', 'term__duration')
I am not sure what the fields are of your Term model, but you would replace name or duration with whichever you are trying to get at.
I think it helps you
terms = Terms.objects.filter(....) # terms
cources0 = terms[0].course_set.all() # courses for terms[0]
cources0 = terms[0].course_set.filter(students=request.user) # courses for terms[0] for user
Related
I am currently working on developing a database and API system where users can create a portfolio which contains a list of coins. I am using Django and I searched everywhere but I kept seeing foreign keys but I'm not sure that's what I need in this situation.
I want two models, one for portfolios which a user will be able to query on, and another coin model which the user will be able to also query on. However in the portfolio there should be a list of coins. I know how to do this in Java using objects but not sure the method in Django.
Here is my model class:
from django.db import models
class Portfolio(models.Model):
name = models.CharField(max_length=250)
def __str__(self):
return self.name
class Coin(models.Model):
name = models.CharField(max_length=100)
symbol = models.CharField(max_length=5)
price = models.DecimalField(max_digits=20, decimal_places=9)
info = models.TextField()
website = models.TextField()
rank = models.IntegerField()
def __str__(self):
return self.name + " - " + self.symbol
Now I would ideally have something like coins = list of Coins model if I was using java to make the objects, but since this is for a database and in Django I'm not sure how I should link the two.
I've seen related objects but did not understand the explanations for my issue. How should I go about setting up these models? Thanks.
It sounds like you want to have a number of Portfolio objects each of which can have varying investments in Coin objects. In this case, you'd want to use a ManyToManyField:
class Portfolio(models.Model):
name = models.CharField(max_length=250)
coins = models.ManyToManyField(Coin)
The database would then store the two dimensional table of which Portfolio holds which coin.
However an alternate approach you could try is to create an object that separately represents the investment:
class Investment(models.Model):
portfolio = models.ForeignKey(Portfolio)
coin = models.ForeignKey(Coin)
bought = models.DateTimeField() # date the investment was made
sold = models.DateTimeField() # date the investment was sold
amount = models.DecimalField() # number of coins held
You could then add a property to Portfolio:
class Portfolio(models.Model):
name = models.CharField(max_length=250)
#property
def coins(self):
return Investment.objects.filter(portfolio=self)
In this way you can not only keep track of which portfolio holds which coins, buy also the entire historical positions too.
I have three models: Assets, AssetTypes and Services. Assets need to get serviced every n months, and have a many-to-one relation with services.
class AssetType(models.Model):
id = models.AutoField(primary_key=True)
name = models.CharField(verbose_name="Asset Type", max_length=100)
service_period = models.PositiveSmallIntegerField(verbose_name="Service Period (in months)", null=True, blank=True, default=12)
class Asset(models.Model):
id = models.AutoField(primary_key=True)
type = models.ForeignKey(AssetType, on_delete=models.PROTECT)
def service_period(self):
return AssetType.objects.get(pk=self.type.id).service_period
def service_history(self):
return self.service_set.all().order_by('-date')
def service_due_date(self):
if self.service_period()==None:
return None
elif self.service_history().count()==0:
return datetime.strptime('2017-01-01', '%Y-%m-%d').date()
else:
last_service_date = self.service_history().latest('date').date
return last_service_date + timedelta(self.service_period()*30)
def service_overdue(self):
return ((self.service_due_date()!=None) and self.service_due_date() < date.today())
class Service(models.Model):
id = models.AutoField(primary_key=True)
date = models.DateField()
asset = models.ForeignKey(Asset, on_delete=models.CASCADE)
I'm trying to work out how to make a query set that would return a list of assets that are overdue for their service. I feel like using a model method is a red herring, and that I would be better off defining a query set filter?
I need the list of overdue assets to be a query set so I can use further query set filters on it.
Any assistance would be greatly appreciated!
So this is a bit tricky.
To put the query in words, you are looking for all Assets whose latest Service date is earlier than today minus the Type's service period multiplied by 30.
To be honest, I would be tempted to denormalize this; you could add a next_service_due field on Asset which is updated when you add a new Service. Then the query is simply all assets with that field less than today.
I am new to Django and I am working on a small module of a Django application where I need to display the list of people who have common interest as that of any particular User. So Suppose if I am an user I can see the list of people who have similar interests like me.
For this I have 2 models :
models.py
class Entity(models.Model):
name = models.CharField(max_length=255, unique=True)
def __str__(self):
return self.name
class UserLikes(models.Model):
class Meta:
unique_together = (('user', 'entity'),)
user = models.ForeignKey(User)
entity = models.ForeignKey(Entity)
def __str__(self):
return self.user.username + " : " + self.entity.name
So in the Entity Table I store the Entities in which user can be interested Eg : football, Music, Code etc.
and in the UserLikes I store the relation about which user likes which entity.
Now I have a Query to fetch details about which user has maximum interest like any particular user :
SELECT y.user_id, GROUP_CONCAT(y.entity_id) likes, COUNT(*) total
FROM likes_userlikes x
JOIN likes_userlikes y ON y.entity_id = x.entity_id AND y.user_id <> x.user_id
WHERE x.user_id = ?
GROUP BY y.user_id
ORDER BY total desc;
Problem is how do I write this Query using Django Querysets and change it into a function.
# this gives you what are current user's interests
current_user_likes = UserLikes.objects.filter(user__id=user_id) \
.values_list('entity', flat=True).distinct()
# this gives you who are the persons that shares the same interests
user_similar_interests = UserLikes.objects.filter(entity__id__in=current_user_likes) \
.exclude(user__id=user_id) \
.values('user', 'entity').distinct()
# finally the count
user_similar_interests_count = user_similar_interests.count()
Here the user_id is the user's id you want to query for.
One advice though, it's not good practice to use plural form for model names, just use UserLike or better, UserInterest for it. Django would add plural form when it needs to.
I have three tables that are related.
class Book(models.Model):
year_published = models.IntField()
author = models.ForeignKey(Author)
class Author(models.Model):
author_id = models.AutoField(primary_key=True)
name = models.CharField(max_length=50)
agent = models.ForeignKey(LitAgent)
class LitAgent(models.Model):
agent_id = models.AutoField(primary_key=True)
name = models.CharField(max_length=50)
Ok, I can get a LitAgent like so
getla = LitAgent.objects.get(agent_id=1)
I can get the authors like so
getauthors = Author.objects.filter(agent=getla.agent_id)
But how can I get all the books that an author has too and make sure the books line up to the right author? I also need access to the data in LitAgent and Author too
From my understanding, you want to get the books by using an agent_id. If this is what you want then you can accomplish this using
books = Book.objects.filter(author__agent__agent_id=1)
This will return a list of all books that the author related to the agent with id = 1. If you want to access the author for each book you can use
for book in books:
print book.author.name
# in order to print the author agent
print book.author.agent.name
On the other side you can reach the books from the LitAgent model.
Lets say
agent = LitAgent.objects.get(agent_id=1)
Then to get the authors it will be
authors = agent.author_set.all()
Now you can iterate
for author in authors:
for book in author.book_set.all()
print book
Hi i'm not very good at English but i'll try to explain myself the best i could. I'm using python and Django to create a web project.
I have this 4 models (this is the best translation i can do of the tables and fields):
class Humans (models.Model):
name = models.CharField(max_length=15)
surname = models.CharField(max_length=15)
doc_num = models.CharField(max_length=11)
...
class Records (models.Model):
closing_state = models.CharField(max_length=2)
...
humans = models.ManyToManyField(Humans, through='Reco_Huma')
class Reco_Huma (models.Model):
id_record = models.ForeignKey(Records)
id_human = models.ForeignKey(Humans)
categorys = models.CharField(max_length=2)
reserv_identity = models.CharField(max_length=2)
repre_entity = models.CharField(max_length=2)
class Observations (models.Model):
id_record = models.ForeignKey(Records)
text = models.CharField(max_length=80)
category = models.CharField(max_length=2, choices=CAT)
Now given a doc_num from Humans, a text from Observations i want to get a QuerySet Of all the Records.
To clarify i first do this:
q1 = Reco_Huma.objects.filter(id_human.doc_num=x)
q2 = Observations.objects.filter(text=y)
both query-sets give me a list of id_record and then i want to connive that lists and filter the Records table with that id_record's
I hope you can understand me
Thanks in advance
To rephrase your query, you want all the Records associated with a certain Human and which have a certain Observation. So it should be:
result = Records.objects.filter(observations__text=y, humans__doc_num=x)
As a general rule, if you want to end up with a certain type of object, it helps to start from there in your query.