NameError: name 'Model' is not defined after importing models in a newly created file

Question

I have created a file called utilities.py within a Django app but I'm getting errors after importing a model from the same app in the file. This is weird because the same file is within the app, I should not be getting that error. Please advise on this.

Here is a screenshot showing where the file is located.

Models

from django.utils import timezone
from django_smalluuid.models import SmallUUIDField, uuid_default
from django.db import models
import pytz
from .utilities import (calc_expiry_date,convert_date)
from monthdelta import monthdelta


class LiquorCostCentre(models.Model):
    cost_centre_id = models.CharField(max_length=250,null=True,blank=True,default="0304-05-05")
    cost_centre_name = models.CharField(max_length=250,null=True,blank=True)

utilities.py

from .models import *

def process_bill(bill_type, liquor_license, cost_centre, account_number_list, description, license_category,user,amount,schedule_type):
    cost_centre_obj, _ = LiquorCostCentre.objects.get_or_create(cost_centre_id=cost_centre)
    bill = LiqourBillTrack.objects.create(
        fee_choice=schedule_type,
        bill_type=bill_type,
        cost_centre=cost_centre_obj.cost_centre_id,
        balance=float(              amount),
        description=description,
        created_by=user,
        year=CURRENT_YEAR,
        liquor_license= liquor_license

    )
    [bill.accounts.add(account_number) for account_number in account_number_list]
    account_values = []
    account_list = bill.accounts.all()
    account_total = [account_values.append(acc_value.amount) for acc_value in account_list ]

    bill_total =sum(account_values)
    bill.total = bill_total
    bill.balance = bill_total
    bill.ref_no = 'LIQ-' + str(NOW.year) + str(NOW.month)+ str(bill.id)
    bill.bill_no = bill.ref_no
    bill.save()
    return bill

Error

eb_1         |   File "/usr/local/lib/python3.7/site-packages/gunicorn/util.py", line 350, in import_app
web_1         |     __import__(module)
web_1         |   File "/app/core/wsgi.py", line 16, in <module>
web_1         |     application = get_wsgi_application()
web_1         |   File "/usr/local/lib/python3.7/site-packages/django/core/wsgi.py", line 12, in get_wsgi_application
web_1         |     django.setup(set_prefix=False)
web_1         |   File "/usr/local/lib/python3.7/site-packages/django/__init__.py", line 24, in setup
web_1         |     apps.populate(settings.INSTALLED_APPS)
web_1         |   File "/usr/local/lib/python3.7/site-packages/django/apps/registry.py", line 112, in populate
web_1         |     app_config.import_models()
web_1         |   File "/usr/local/lib/python3.7/site-packages/django/apps/config.py", line 198, in import_models
web_1         |     self.models_module = import_module(models_module_name)
web_1         |   File "/usr/local/lib/python3.7/importlib/__init__.py", line 127, in import_module
web_1         |     return _bootstrap._gcd_import(name[level:], package, level)
web_1         |   File "/app/liquor/models.py", line 10, in <module>
web_1         |     from .utilities import (calc_expiry_date,convert_date)
web_1         |   File "/app/liquor/utilities.py", line 2, in <module>
web_1         |     from liquor.models import LiquorCostCentre
web_1         | ImportError: cannot import name 'LiquorCostCentre' from 'liquor.models' (/app/liquor/models.py)
web_1         | [2020-02-17 11:19:23 +0300] [17] [INFO] Worker exiting (pid: 17)
web_1         | Sentry is attempting to send 0 pending error messages
web_1         | Waiting up to 2 seconds
web_1         | Press Ctrl-C to quit
web_1         | [2020-02-17 11:19:26 +0300] [14] [INFO] Shutting down: Master
web_1         | [2020-02-17 11:19:26 +0300] [14] [INFO] Reason: Worker failed to boot.

Solution 1

To fix your trouble(cross imports) you need to make import inside functions:

def process_bill(bill_type, liquor_license, cost_centre, account_number_list, description, license_category,user,amount,schedule_type):
    from .models import LiquorCostCentre, LiqourBillTrack
    # YOUR CODE HERE

and REMOVE import * from top of the utilities.py and of cause if you need some others models in your utilities code, put they import inside functions.

Solution 2

Issue is of circular import.

You are importing from .utilities import (calc_expiry_date,convert_date) in models.py and then in utilities.py, you are importing

This is a classic case of circular import.

Solution is to import locally i.e

def process_bill(bill_type, liquor_license, cost_centre, account_number_list, description, license_category,user,amount,schedule_type):
    from models import LiquorCostCentre, LiqourBillTrack
    cost_centre_obj, _ = LiquorCostCentre.objects.get_or_create(cost_centre_id=cost_centre)
    bill = LiqourBillTrack.objects.create(
        fee_choice=schedule_type,
        bill_type=bill_type,
        cost_centre=cost_centre_obj.cost_centre_id,
        balance=float(              amount),
        description=description,
        created_by=user,
        year=CURRENT_YEAR,
        liquor_license= liquor_license

    )
    [bill.accounts.add(account_number) for account_number in account_number_list]
    account_values = []
    account_list = bill.accounts.all()
    account_total = [account_values.append(acc_value.amount) for acc_value in account_list ]

    bill_total =sum(account_values)
    bill.total = bill_total
    bill.balance = bill_total
    bill.ref_no = 'LIQ-' + str(NOW.year) + str(NOW.month)+ str(bill.id)
    bill.bill_no = bill.ref_no
    bill.save()
    return bill

Comments

[Sachin]

Did you try importing that specific model instead of "*"?

[Brown Bear]

show code where you define the models, and please put the error output as text

[asad_hussain]

Error log says File "/app/liquor/utilities.py", line 2, in <module> web_1 | from liquor.models import LiquorCostCentre

[Philip Mutua]

@Sachin Imported without the asterisk "*" but I'm getting the same error

[Brown Bear]

you have cross import error

[Philip Mutua]

@BearBrown How can this be resolved? I have a different branch that is working perfectly and I'm importing the same way using from .models import * in utilities.py

[Philip Mutua]

issued resolved, it's working! learned something valuable today :)

[Brown Bear]

glad to help you!