Django - Circular model import issue
I'm really not getting this, so if someone could explain how this works I'd very much appreciate it. I have two applications, Accounts and Theme... here is my settings list:
INSTALLED_APPS = (
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'accounts',
'themes',
)
In accounts, I am trying to do this:
from themes.models import Theme
class Account(models.Model):
ACTIVE_STATUS = 1
DEACTIVE_STATUS = 2
ARCHIVE_STATUS = 3
STATUS_CHOICES = (
(ACTIVE_STATUS, ('Active')),
(DEACTIVE_STATUS, ('Deactive')),
(ARCHIVE_STATUS, ('Archived')),
)
id = models.AutoField(primary_key=True)
name = models.CharField(max_length=250)
slug = models.SlugField(unique=True, verbose_name='URL Slug')
status = models.IntegerField(choices=STATUS_CHOICES, default=ACTIVE_STATUS, max_length=1)
owner = models.ForeignKey(User)
enable_comments = models.BooleanField(default=True)
theme = models.ForeignKey(Theme)
date_created = models.DateTimeField(default=datetime.now)
And in my theme model:
class Theme(models.Model):
id = models.AutoField(primary_key=True)
name = models.CharField(max_length=250)
slug = models.SlugField(unique=True, verbose_name='URL Slug')
date_created = models.DateTimeField(default=datetime.now)
class Stylesheet(models.Model):
id = models.AutoField(primary_key=True)
account = models.ForeignKey(Account)
date_created = models.DateTimeField(default=datetime.now)
content = models.TextField()
Django is kicking out the following error:
from themes.models import Theme
ImportError: cannot import name Theme
Is this some kind of circular import issue? I've tried using a lazy reference, but that doesn't seem to work either!
Account from the module where Theme is defined?
Remove the import of Theme and use the model name as a string instead.
theme = models.ForeignKey('themes.Theme')
Upto Django 1.7:
Use get_model function from django.db.models which is designed for lazy model imports.:
from django.db.models import get_model
MyModel = get_model('app_name', 'ModelName')
In your case:
from django.db.models import get_model
Theme = get_model('themes', 'Theme')
Now you can use Theme
For Django 1.7+:
from django.apps import apps
apps.get_model('app_label.model_name')
Something I haven't seen mentioned anywhere in sufficient detail is how to properly formulate the string inside ForeignKey when referencing a model in a different app. This string needs to be app_label.model_name. And, very importantly, the app_label is not the entire line in INSTALLED_APPS, but only the last component of it. So if your INSTALLED_APPS looks like this:
INSTALLED_APPS = (
...
'path.to.app1',
'another.path.to.app2'
)
then to include a ForeignKey to a model in app2 in an app1 model, you must do:
app2_themodel = ForeignKey('app2.TheModel')
I spent quite a long time trying to solve a circular import issue (so I couldn't just from another.path.to.app2.models import TheModel) before I stumbled onto this, google/SO was no help (all the examples had single component app paths), so hopefully this will help other django newbies.
Since Django 1.7 correct way is to go like this:
from django.apps import apps
YourModel = apps.get_model('your_app_name', 'YourModel')
See: https://docs.djangoproject.com/ja/1.9/ref/applications/#django.apps.apps.get_model
apps.get_model('your_app_name.YourModel') convenient for use in a map etc.
I had the same problem but on using MyModel = get_model('app_name', 'ModelName') I got a new error 'raise AppRegistryNotReady("Models aren't loaded yet.")'
I tried all the other methods on this page but none worked for me. The way I fixed it was to use: MyModel = get_model('app_name', 'ModelName') but actually in the class rather than outside of it.
from django.apps import apps I then defined a save method which inside has: Cart = apps.get_model(app_label='Carts', model_name='Cart') This allows me to import another django model from elsewhere.
This is how I fix the circular issue by specifying 'app_name.model_name' and TYPE_CHECKING
profile app's models.py
from typing import TYPE_CHECKING
if TYPE_CHECKING:
from team.models import Team
team = models.ForeignKey('team.Team',...)
team app's models.py
Class Team
name = models.CharField(...)
head = models.ForeignKey('profile.Profile',...)
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'themes.Theme', as it's in a different app.