ImportError: cannot import name '...' from partially initialized module '...' (most likely due to a circular import)

I'm upgrading an application from Django 1.11.25 (Python 2.6) to Django 3.1.3 (Python 3.8.5) and, when I run manage.py makemigrations, I receive this messasge:

File "/home/eduardo/projdevs/upgrade-intra/corporate/models/section.py", line 9, in <module>
from authentication.models import get_sentinel**


ImportError: cannot import name 'get_sentinel' from partially initialized module 'authentication.models' (most likely due to a circular import) (/home/eduardo/projdevs/upgrade-intra/authentication/models.py)**

My models are:

authentication / models.py

from django.conf import settings
from django.contrib.auth.models import AbstractUser, UserManager
from django.db import models
from django.db.models.signals import post_save
from django.utils import timezone


from corporate.constants import GROUP_SUPPORT
from corporate.models import Phone, Room, Section
from library.exceptions import ErrorMessage
from library.model import update_through_dict
from .constants import INTERNAL_USER, EXTERNAL_USER, SENTINEL_USERNAME, SPECIAL_USER, USER_TYPES_DICT




class UserProfile(models.Model):
user = models.OneToOneField(
'User',
on_delete=models.CASCADE,
unique=True,
db_index=True
)
...
phone = models.ForeignKey('corporate.Phone', on_delete=models.SET_NULL, ...)
room = models.ForeignKey('corporate.Room', on_delete=models.SET_NULL, ...)
section = models.ForeignKey('corporate.Section', on_delete=models.SET_NULL, ...)
objects = models.Manager()
...


class CustomUserManager(UserManager):


def __init__(self, type=None):
super(CustomUserManager, self).__init__()
self.type = type


def get_queryset(self):
qs = super(CustomUserManager, self).get_queryset()
if self.type:
qs = qs.filter(type=self.type).order_by('first_name', 'last_name')
return qs


def get_this_types(self, types):
qs = super(CustomUserManager, self).get_queryset()
qs = qs.filter(type__in=types).order_by('first_name', 'last_name')
return qs


def get_all_excluding(self, types):
qs = super(CustomUserManager, self).get_queryset()
qs = qs.filter(~models.Q(type__in=types)).order_by('first_name', 'last_name')
return qs


class User(AbstractUser):
type = models.PositiveIntegerField('...', default=SPECIAL_USER)
username = models.CharField('...', max_length=256, unique=True)
first_name = models.CharField('...', max_length=40, blank=True)
last_name = models.CharField('...', max_length=80, blank=True)
date_joined = models.DateTimeField('...', default=timezone.now)
previous_login = models.DateTimeField('...', default=timezone.now)


objects = CustomUserManager()
...
def get_profile(self):
if self.type == INTERNAL_USER:
...
return None


def get_or_create_profile(self):
profile = self.get_profile()
if not profile and self.type == INTERNAL_USER:
...
return profile


def update(self, changes):
...


class ExternalUserProxy(User):
objects = CustomUserManager(type=EXTERNAL_USER)


class Meta:
proxy = True
verbose_name = '...'
verbose_name_plural = '...'


class InternalUserProxy(User):
objects = CustomUserManager(type=INTERNAL_USER)


class Meta:
proxy = True
verbose_name = '...'
verbose_name_plural = '...'


def create_profile(sender, instance, created, **kwargs):
if created and instance.type == INTERNAL_USER:
try:
profile = UserProfile()
profile.user = instance
profile.save()
except:
pass


post_save.connect(create_profile, sender=User)


def get_sentinel():
try:
sentinel = User.objects.get(username__exact=SENTINEL_USERNAME)
except User.DoesNotExist:
settings.LOGGER.error("...")
from django.contrib.auth.models import Group
sentinel = User()
sentinel.username = SENTINEL_USERNAME
sentinel.first_name = "..."
sentinel.last_name = "..."
sentinel.set_unusable_password()
sentinel.save()
technical = Group.objects.get(name=GROUP_SUPPORT)
sentinel = User.objects.get(username__exact=SENTINEL_USERNAME)
sentinel.groups.add(technical)
sentinel.save()
return sentinel

corporate / models / __init__.py

...
from .section import Section
...

corporate / models / section.py

from django.conf import settings
from authentication.models import get_sentinel
from .room import Room


class Section(models.Model):
...
boss = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.SET(get_sentinel), ...)
surrogate = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.SET(get_sentinel), ...)
room = models.ForeignKey(Room, on_delete=models.SET_NULL, ...)
is_subordinate_to = models.ForeignKey('self', on_delete=models.SET_NULL, ...)
...

What am I doing wrong?

204054

小开

最佳答案

You have a circular import.

authentication/models imports corporate/models, which imports corporate/models/section, which imports authentication/models.

You can't do that.

小开

For future readers, this can also happen if you name a python file the same name as a dependency your project uses.

For example:

I cannot have a file named retrying.py that is using the retrying package.

Assuming I had the retrying package in my project, I could not have a file called retrying.py with the below contents:

from retrying import retry
print("HI")

A similar error with the message "most likely due to a circular import" would occur.

The same contents would work fine if I renamed the file to "retrying_example1.py"

小开

When importing code from other files, it helps if you spell out the entire subpackage where the thing you want to import comes from. Let's say you have the following file structure:

mypackage/
subpackage/
__init__.py
helper.py
main/
work.py

If:

__init__.py imports things from helper.py (for the end-user to conveniently access)
and you're working inside work.py
and you need something from subpackage/helper.py

Then rather than doing:

from ..subpackage import thing_i_need

You should instead do:

from ..subpackage.helper import thing_i_need

For reasonable code, this should help you avoid some of the circular dependency problems, as now you're no longer relying on __init__.py to fully finish.

小开

In my case the problem was that I defined the function in the x.py file and in the x.py file I import models from the modals.py file and in the modals.py file I tried to import this function I was trying to set the default value after querying the tables with this function

小开

I received this error when I tried to do a relative import. I had two models files:

utils.models:

class BaseModel(models.Model):
...

main.models:

from .models import BaseModel
...

The problem was fixed when, in main.models, I changed it to:

from utils.models import BaseModel

小开

One way to resolve circular imports is by splitting a file in the circle into multiple files in such a way that the files are no longer importing each other. In this specific case, I think it would be resolved if get_sentinel was moved to a separate file.

authentication / models_utils.py

def get_sentinel():
...

corporate / models / section.py

from django.conf import settings
from authentication.models_utils import get_sentinel
from .room import Room


class Section(models.Model):
...

小开

I got the same error below:

AttributeError: partially initialized module 'math' has no attribute 'pi' (most likely due to a circular import)

Because I created math.py, imported python's math module in it and use math.pi in it as shown below:

# "math.py"


import math


print(math.pi)

So, I changed math.py to my_math.py:

# "my_math.py"


import math


print(math.pi)

Then, the error was solved:

3.141592653589793