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Delete 2 model different objects which reference each other as foreign keys

We have two Django models:
class Project(models.Model):
project_title = models.CharField(max_length=30)
owner = models.ForeignKey(User, null=True, on_delete=models.DO_NOTHING)
class User(models.Model):
usernmae = models.CharField(max_length=50)
active_project = models.ForeignKey(User, null=True, on_delete=models.DO_NOTHING, related_name='current_project')
I have a user with object (with id say 692). And this user created a project with id=12345, therefore these owner field will get have this particular referenced.
I want to delete that user. But it shows error that
delete on table "app_user" violates foreign key constraint
This is expected as on_delete=models.DO_NOTHING, was set. One way I found out was using on_delete=models.CASCADE.
Question: How should I go about deleting the user (692) without changing the model definition(having to re-run migration)?
Doing it manually by deleting the project first, leads to the same foreign-key error, as owner field is User object.
How to handle this mutual foreign key relationship while deleting, as deleting any one of those two throws the foreign-key exception?
Update
Some correction in the model definition username is the field name instead of usernmae (typo). And the foreignkey for project is Project not the User model.
class Project(models.Model):
project_title = models.CharField(max_length=30)
owner = models.ForeignKey(User, null=True, on_delete=models.DO_NOTHING)
class User(models.Model):
username = models.CharField(max_length=50)
active_project = models.ForeignKey(Project, null=True, on_delete=models.DO_NOTHING, related_name='current_project')

IF you really don't want to make a migration (any specific reason?) and if you are ok with doing this manually this time. Then you have two options:
Go into the admin panel and manually change the User field in the project instance to a different user or to NULL. Now you should be able to delete the User instance since it's not referred anymore into the project.
If that worked, you can then delete the project instane as well.
Curios if this will work, let me know!

Django Operational Error: foreign key mismatch

I have two models:
from django.db import models
from django.contrib.auth.models import User
# Create your models here.
class Category(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="categories")
name = models.CharField(max_length=30, unique=True, primary_key=True)
class Todo(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='todos')
# TODO: Add confirmation before deleting category
category = models.ForeignKey(Category, on_delete=models.CASCADE,
related_name="todos_in_category", null=True)
item = models.CharField(max_length=50)
added = models.DateTimeField(auto_now_add=True)
completed = models.BooleanField(default=False)
Previously, Category's PK was the default id, however, I changed it to the name field. When I ran the migrations, i received the operational error. Thinking that it was perhaps due to a conflict between the existing id fields and the new primary key, I cleared the data in the database but with no success. Any ideas as to what could be the issue here? Thanks!

How to insert data into a relational one to one table in django?

I have a UserProfile table which is in relation with the default Django User table. Here's how it looks.
class UserProfile(models.Model):
user = user.OneToOneField(User, on_delete=models.CASCADE)
section = models.CharField(max_length=255, blank=True)
year = models.IntegerField(null=True, blank=True)
course = models.CharField(max_length=255, blank=True)
qrcode = models.CharField(max_length=255, blank=True)
present = models.BooleanField(default=False)
I am trying to insert the data into the UserProfile table using the Django Shell.
from users.models import UserProfile
a = UserProfile(qrcode="hello")
a.save()
This is how I have always known to insert data into tables, it has always worked. BUT when i try to do this in UserProfile model. I get this exception. NOT NULL constraint failed: users_userprofile.user_id. Which in turn is caused by the following exception Error in formatting: RelatedObjectDoesNotExist: UserProfile has no user.
I somewhat understand that I somehow need to supply a user instance. But I am clueless as to how. Can someone please help me.

Firstly you need to create User.
u1 = User(username='user1')
u1.save()
Create a UserProfile. Pass the ID of the “parent” object as this object’s ID:
v1 = UserProfile(user=u1, ....)
v1.save()
refer this

You need to create your User first
user = User.objects.create(username='user')
and then you can do:
user_profile = UserProfile.objects.create(user=user, ...)

Django (DRF) Boolean Field missing in JSON

I'm writing a rather simple REST API using Django REST Framework. I am trying to add a boolean field to my model that would show if it is publicly accessible or not.
In my models.py, my model looks like this:
class BlogPost(models.Model):
title = models.CharField(max_length=20, default='', blank=False)
description = models.CharField(max_length=140, default='', blank=False)
is_public = models.BooleanField(default=True, blank=False)
Then in my serializers.py, my serializer for the model looks like this:
class BlogPostSerializer(serializers.ModelSerializer):
class Meta:
model = BlogPost
fields = ('title', 'description', 'is_public')
However, when I create an instance of that model, and run my development server, the JSON only returns the title and the description. The is_public field is missing from the JSON.
I've searched everywhere and can't find the reason for this odd problem.
Any help would be much appreciated!

Django ManyToMany Field with an already existing table

What I'm trying to achieve is, having model Person that is created and managed by Django have a ManyToMany field with model Property that was "created" using inspectdb and already exists in the database.
(Property contains Geographical data and cannot be managed or changed by Django)
When trying to migrate, it raises :
ValueError: Related model 'cadastroapp.Property' cannot be resolved
Full stack here
Worth nothing that I removed from the migration file the step to create model Property, since it already exists and AFAIK there's no way to tell Django this in the model Class
models.py (simplified) :
class Person(models.Model):
objectid = models.AutoField(primary_key=True)
properties = models.ManyToManyField(
'Property',
through = 'Person_Property',
)
class Meta:
db_table = 'django_person'
class Person_Property(models.Model):
cod_person = models.ForeignKey('Person', on_delete=models.CASCADE)
cod_property = models.ForeignKey('Property', on_delete=models.CASCADE)
class Meta:
db_table = 'django_person_property'
class Property(models.Model):
objectid = models.BigIntegerField(unique=True, primary_key=True)
created_user = models.CharField(max_length=765, blank=True, null=True)
created_date = models.DateTimeField(blank=True, null=True)
last_edited_user = models.CharField(max_length=765, blank=True, null=True)
last_edited_date = models.DateTimeField(blank=True, null=True)
shape = models.TextField(blank=True, null=True) # This field type is a guess. - ESRI Shape
class Meta:
managed = False
db_table = '"GEO"."PROPERTY"'

There are a couple errors in your models.py file.
When defining a Foreignkey or ManytoMany field, you don't want the model name to be in quotes.
Please change:
class Person(models.Model):
properties = models.ManyToManyField(
'Property',
through = 'Person_Property',
)
and
class Person_Property(models.Model):
cod_person = models.ForeignKey('Person', on_delete=models.CASCADE)
cod_property = models.ForeignKey('Property', on_delete=models.CASCADE)
to:
class Person(models.Model):
properties = models.ManyToManyField(
Property,
through = 'Person_Property',
)
and
class Person_Property(models.Model):
cod_person = models.ForeignKey(Person, on_delete=models.CASCADE)
cod_property = models.ForeignKey(Property, on_delete=models.CASCADE)
then delete your migration file cadastroapp.0006_auto_20161122_1533.
then run makemigrations and migrate again.
This may still not migrate without errors, but it will get us on the right track.

I think that you want to put the model name in quotes. In case you leave it without quotes you have to ensure that the model is defined before the ManyToMany field has been defined. So you will need to have first class Property and then class Person in your file. When you put model name as "Property" then you do not need to care about order of class definitions.