AttributeError when I import model from another app - django

Question

I don't know why but I got an error: AttributeError: module 'downloads.models' has no attribute 'AbstractDownload' in this place: class Download(models_downloads.AbstractDownload):
In download app I have already AbstractDownload class
Here is my model from products
products/models.py
from downloads import models as models_downloads
class Download(models_downloads.AbstractDownload):
product = models.ForeignKey('products.Product', related_name='downloads')
file = FilerFileField(related_name="file_products_download")
Here is downloads models
downloads/models.py
class AbstractDownload(models.Model):
title = models.CharField(max_length=500)
subtitle = models.CharField(max_length=1000, blank=True)
file = FilerFileField(related_name="file_abstract_download")
order = models.PositiveIntegerField(default=0)
class Meta:
abstract = True
def __str__(self):
return self.title
Traceback:
Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/path/venv/lib/python3.5/site-packages/django/core/management/__init__.py", line 363, in execute_from_command_line
utility.execute()
File "/path/venv/lib/python3.5/site-packages/django/core/management/__init__.py", line 337, in execute
django.setup()
File "/path/venv/lib/python3.5/site-packages/django/__init__.py", line 27, in setup
apps.populate(settings.INSTALLED_APPS)
File "/path/venv/lib/python3.5/site-packages/django/apps/registry.py", line 108, in populate
app_config.import_models()
File "/path/venv/lib/python3.5/site-packages/django/apps/config.py", line 202, in import_models
self.models_module = import_module(models_module_name)
File "/path/venv/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/www/downloads/models.py", line 6, in <module>
from products import models as products_models
File "/path/www/products/models.py", line 31, in <module>
class Download(models_downloads.AbstractDownload):
AttributeError: module 'downloads.models' has no attribute 'AbstractDownload'

Answer 1

You have a circular import. Your downloads/models.py has:
from products import models as products_models
But your products/models.py has
from downloads import models as models_downloads
You haven't shown how you use products_models, so we can't really say how to fix it. Here's a few suggestions:
Perhaps that import isn't necessary if you use a string for foreign keys, e.g. models.ForeignKey('downloads.ModelName')
Perhaps you could move AbstractDownload and Download so that they are in the same models, so that you don't need an import
If you use products_models inside a method, you could move the import inside the method. I would avoid this if possible.