def __str__(self) issue - Django - python

I'm trying to print the title of the first object in my DB in django. However, when I enter the command
Project.objects.all() in the shell, it just returns the following:
<QuerySet [<Project: Project object (1)>]>
This is my code:
# Create your models here.
class Project(models.Model):
title = models.CharField(max_length=100)
progress = models.FloatField(default=0)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
def __str__(self):
return self.title
class Task(models.Model):
project = models.ForeignKey(Project, on_delete=models.CASCADE)
title = models.CharField(max_length=100)
priority = models.SmallIntegerField(default=0)
open_date = models.DateTimeField()
close_date = models.DateTimeField()
status = models.SmallIntegerField(default=0)
def __str__(self):
return self.title
The str part doesn't seem to be doing anything, even when I purposely misspell something, no error is returned. There seems to be a few threads with similar issues with no accepted solutions as of yet.
I would like it to return the title that I've entered, which should be <QuerySet [<Project: My First Project>]>.
Thanks in advance for your help.


You are passing self.title to the str method. Just pass self and then return the title.
def __str__(self):
return self.title


Typically, the repr of underlying objects is used when printing their containers (all the built-in collections types do this for instance). Change the name of the method from __str__ to __repr__ and it should fix your issue. __str__ already defaults to using the __repr__ method if no other __str__ is defined, so it'll still work in other stringifying scenarios.

Related

Name issue. Can't change the name of the Models in django database

from django.db import models
# Create your models here.
class Course (models.Model):
name = models.CharField(max_length=100)
language= models.CharField(max_length=100)
price= models.CharField(max_length=100)
def __str__(self):
return self.name
in django database the object dosent change name still named Course object (1) in the list. Why does it not change? def str(self):
return self.name
what should one do to make django show the courses names? This should be correct. no errors or anything it just simply dosent do what it should. it seems strange.

The __str__ function should be in your class, not after it
class Course(models.Model):
name = models.CharField(max_length=100)
language = models.CharField(max_length=100)
price = models.CharField(max_length=100)
def __str__(self):
return self.name

class Course(models.Model):
name = models.CharField(max_length=100)
language= models.CharField(max_length=100)
price= models.CharField(max_length=100)
def __str__(self):
return self.name

i got answer for this so you have to add this in respective modules like i have category module in which models.py and then add this method.

What is doing __str__ function in Django? [duplicate]

This question already has answers here:
What is the difference between __str__ and __repr__?
(28 answers)
Closed last month.
I'm reading and trying to understand django documentation so I have a logical question.
There is my models.py file:
from django.db import models
class Blog(models.Model):
name = models.CharField(max_length=255)
tagline = models.TextField()
def __str__(self):
return self.name
class Author(models.Model):
name = models.CharField(max_length=255)
email = models.EmailField()
def __str__(self):
return self.name
class Post(models.Model):
blog = models.ForeignKey(Blog)
headline = models.CharField(max_length=255)
body_text = models.TextField()
pub_date = models.DateField()
mod_date = models.DateField()
authors = models.ManyToManyField(Author)
n_comments = models.IntegerField()
n_pingbacks = models.IntegerField()
rating = models.IntegerField()
def __str__(self):
return self.headline
What is doing here each __str__ function in each class?
What is the reason I need those functions in it?

You created a Blog model. Once you migrate this, Django will create a table with "name" and "tagline" columns in your database.
If you want to interact with the database with the model, for example create an instance of the model and save it or retrieve the model from db,
def __str__(self):
return self.name
will come handy. Open the python interactive shell in your project's root folder via:
python manage.py shell
Then
from projectName.models import Blog
Blog.objects.all() # will get you all the objects in "Blog" table
Also, when you look at the models in your admin panel, you will see your objects listed, with the name property.
The problem is, the return will look like this if you did not add that function:
<QuerySet [<Blog:>,<Blog:>,<Blog:>....]
So you will not know what those objects are. A better way to recognize those objects is retrieving them by one of its properties which you set it as name. This way you will get the result as follow:
<QuerySet [<Blog:itsName>,<Blog:itsName>,<Blog:itsName>....]
If you want to test this out, run python manage.py shell and run:
from projectName.models import Blog
# The below will create and save an instance.
# It is a single step. Copy-paste multiple times.
Blog.objects.create(name="first",tagline="anything")
Blog.objects.all() # check out the result

The __str__ method just tells Django what to print when it needs to print out an instance of the any model. It is also what lets your admin panel, go from this
Note: how objects are just plainly numbered
to this
.
Note: proper object names here
You could choose what to show in the admin panel, as per your choice. Be it a field value or a default value or something else.

This overrides the default name of the objects of this class, it's something like Author:object which isn't very helpful.
overriding it gives a more human friendly name of the object like the Author.name

def str(self): is a python method which is called when we use print/str to convert object into a string. It is predefined , however can be customised. Will see step by step.Suppose below is our code.
class topics():
def __init__(self,topics):
print "inside init"
self.topics=topics
my_top = topics("News")
print(my_top)
Output:
inside init
<__main__.topics instance at 0x0000000006483AC8>
So while printing we got reference to the object. Now consider below code.
class topics():
def __init__(self,topics):
print "inside init"
self.topics=topics
def __str__(self):
print "Inside __str__"
return "My topics is " + self.topics
my_top = topics("News")
print(my_top)
Output:
inside init
Inside __str__
My topics is News
So, here instead of object we are printing the object. As we can see we can customize the output as well. Now, whats the importance of it in a django models.py file?
When we use it in models.py file, go to admin interface, it creates object as "News", otherwise entry will be shown as main.topics instance at 0x0000000006483AC8 which won't look that much user friendly.

The __str__ function is used add a string representation of a model's object, so that is
to tell Python what to do when we convert a model instance into a string.
And if you dont mention it then it will take it by default the USERNAME_FIELD for that purpose.
So in above example it will convert Blog and Author model's object to their associated name field and the objects of Post model to their associated headline field

Django has __str__ implementations everywhere to print a default string representation of its objects. Django's default __str__ methods are usually not very helpful. They would return something like Author object (1). But that's ok because you don't actually need to declare that method everywhere but only in the classes you need a good string representation. So, if you need a good string representation of Author but not Blog, you can extend the method in Author only:
class Author(models.Model):
name = models.CharField(max_length=100)
...
def __str__(self):
return f'{self.name}' # This always returns string even if self.name is None
class Post(models.Model):
author = models.ForeignKey(Author, on_delete=models.CASCADE)
text = models.CharField(max_length=100)
author = Author.objects.create(name='David')
print(author) # David
post = Post.objects.create(author=author, text='some text')
print(post) # Post object(1)
Now, beyond Django, __str__ methods are very useful in general in Python.
More info here.

When you want to return the objects in that class then you'll see something such as <QuerySet [object(1)]>. However no body wants to see something like this. they want actual name that human can understand what exactly is present in that table, so they use this function.

For example, you define __str__() in Person model as shown below:
# "models.py"
from django.db import models
class Person(models.Model):
first_name = models.CharField(max_length=20)
last_name = models.CharField(max_length=20)
def __str__(self): # Here
return self.first_name + " " + self.last_name
Then, you define Person admin as shown below:
# "admin.py"
from django.contrib import admin
from .models import Person
#admin.register(Person)
class PersonAdmin(admin.ModelAdmin):
pass
Now, the full name is displayed in the message and list in "Change List" page:
And in "Change" page:
And in "Delete" page:
Next, if you don't define __str__() in Person model as shown below:
# "models.py"
from django.db import models
class Person(models.Model):
first_name = models.CharField(max_length=20)
last_name = models.CharField(max_length=20)
# def __str__(self): # Here
# return self.first_name + " " + self.last_name
Now, the object name and id are displayed in the message and list in "Change List" page:
And in "Change" page:
And in "Delete" page:

when I use object name I get 'DeferredAttribute' object has no attribute 'get'

I'm new with django. I'm really confused with views filters.
Here is my models.py:
class Author(models.Model):
title = models.CharField(max_length=30)
user=models.ForeignKey(User)
age= models.CharField(max_length=2)
post= models.ManyToManyField(Article)
def __str__(self):
return self.title
def __str__(self):
return self.post
def __str__(self):
return self.age
class Meta:
ordering = ('title','user',)
Here is my views.py:
def posting(request):
details = Author.age.get(pk=request.user.id)
return render(request,'home.html' , {'detail':details})
Now I need to get the current logged in user (age or title or post). When I execute the code I get the above error. How can I filter the particular object of logged in user?
Kindly suggest me some docs for views filter.

You access fields after returning a model instance via the manager (default manager is named objects), not directly:
author = Author.objects.get(user=request.user)
age = author.age
Talking about some docs, the Django documentation is a good starting point.

Django Admin showing Object - not working with __unicode__ OR __str__

my Django admin panel is showing object instead of self.name of the object.
I went through several similar questions here yet couldn't seem to resolve this issue. __unicode__ and __str__ bear the same results, both for books and for authors. I've changed those lines and added new authors/books in every change but no change.
MODELS.PY
from django.db import models
from django.contrib.auth.models import User
# Create your models here.
class Author(models.Model):
name = models.CharField(max_length=100)
def __str__(self):
return self.name
class Book(models.Model):
auto_increment_id = models.AutoField(primary_key=True)
name = models.CharField('Book name', max_length=100)
author = models.ForeignKey(Author, blank=False, null=False)
contents = models.TextField('Contents', blank=False, null=False)
def __unicode__(self):
return self.name
I used both unicode & str interchangeably, same result.
Here are the screenshots of the admin panel by menu/action.
1st screen
Author List
Single Author

Your indentation is incorrect. You need to indent the code to make it a method of your model. It should be:
class Author(models.Model):
name = models.CharField(max_length=100)
def __str__(self):
return self.name
If you are using Python 3, use __str__. If you are using Python 2, use __unicode__, or decorate your class with the python_2_unicode_compatible decorator. After changing the code, make sure you restart the server so that code changes take effect.

Django get attributes from foreign key's class

I would like to show one attribute from another class. The current class has a foreign key to class where I want to get the attribute.
# models.py
class Course(models.Model):
name = models.CharField(max_length=100)
degree = models.CharField(max_length=15)
university = models.ForeignKey(University)
def __unicode__(self):
return self.name
class Module(models.Model):
code = models.CharField(max_length=10)
course = models.ForeignKey(Course)
def __unicode__(self):
return self.code
def getdegree(self):
return Course.objects.filter(degree=self)
# admin.py.
class ModuleAdmin(admin.ModelAdmin):
list_display = ('code','course','getdegree')
search_fields = ['name','code']
admin.site.register(Module,ModuleAdmin)
So what i'm trying to do is to get the "degree" that a module has using the "getdegree". I read several topics here and also tried the django documentation but i'm not an experienced user so even I guess it's something simple, I can't figure it out. Thanks!

It is pretty straight forward.
Try this:
def getdegree(self):
return self.course.degree
Documentation here
You can do this safely because course is not a nullable field. If it were, you should have checked for existence of object before accessing its attribute.

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