Re: RuntimeError: Model class polls38.polls.models.Question doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

you may also need to change polls/apps.py to have a config class

On Thu, Dec 3, 2020 at 5:31 PM Ryan Gedwill <ryangedwill@gmail.com> wrote:

you at least need to add 'polls' to your INSTALLED_APPS in settings.py. You should also remove the line you put in manage.py - that file should rarely be touched at all.

This is not a system path problem

On Thu, Dec 3, 2020 at 12:38 PM Ennio Santos <ennio.gomide@gmail.com> wrote:

I developed some small web app using Django, but I had not used virtual env up to the moment.

I am facing the erro above, I can imagine that is related to some kind of path definition  that is not properly defined, but have no idea where to begin.

My Env

windows 10 home

Currently using CONDA, version 4.9.2, installed on my "C" driver. 

# conda environments:

#

base                     C:\ProgramData\Anaconda3

pranos39                 C:\ProgramData\Anaconda3\envs\pranos39

agen37                   C:\Users\ennio\.conda\envs\agen37

agen39                   C:\Users\ennio\.conda\envs\agen39

baseold                  C:\Users\ennio\.conda\envs\baseold

python38                 C:\Users\ennio\.conda\envs\python38

                            *  d:\conda_env\py38 (this is the one I activate)

And the editor is vscode 1.51.1 version. using pylint, and it is pointing to the python env above.

I have the driver "D" where is the conda env being used. And also, where is the source code.

D:\Linguagem\mooc\code\polls38

Tutorial being used

since it is the first time using the virtual env to build a django app, I decide to use the tutorial available to test:

Writing your first Django app, part 1 | Django documentation | Django (djangoproject.com) 

Using the exemplo, as it is.

 (d:\conda_env\py38) D:\Linguagem\mooc\code\polls38>conda list

# packages in environment at d:\conda_env\py38:

#

# Name                    Version                   Build  Channel

asgiref                   3.3.1              pyhd3eb1b0_0

astroid                   2.4.2                    py38_0

ca-certificates           2020.10.14                    0

certifi                   2020.11.8        py38haa95532_0

colorama                  0.4.4                      py_0

django                    3.1.3              pyhd3eb1b0_0

isort                     5.6.4                      py_0

krb5                      1.17.1               hc04afaa_0

lazy-object-proxy         1.4.3            py38he774522_0

libpq                     12.2                 h3235a2c_0

mccabe                    0.6.1                    py38_1

openssl                   1.1.1h               he774522_0

pip                       20.3             py38haa95532_0

psycopg2                  2.8.5            py38h7a1dbc1_0

pylint                    2.6.0                    py38_0

python                    3.8.5                h5fd99cc_1

pytz                      2020.4             pyhd3eb1b0_0

setuptools                50.3.1           py38haa95532_1

six                       1.15.0           py38haa95532_0

sqlite                    3.33.0               h2a8f88b_0

sqlparse                  0.4.1                      py_0

tk                        8.6.10               he774522_0

toml                      0.10.1                     py_0

vc                        14.1                 h0510ff6_4

vs2015_runtime            14.16.27012          hf0eaf9b_3

wheel                     0.35.1             pyhd3eb1b0_0

wincertstore              0.2                      py38_0

wrapt                     1.11.2           py38he774522_0

zlib                      1.2.11               h62dcd97_4

The settings.py file

from pathlib import Path

# Build paths inside the project like this: BASE_DIR / 'subdir'.

BASE_DIR = Path(__file__).resolve().parent.parent

print(BASE_DIR)

# Quick-start development settings - unsuitable for production

# See https://docs.djangoproject.com/en/3.1/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!

SECRET_KEY = '********'

# SECURITY WARNING: don't run with debug turned on in production!

DEBUG = True

ALLOWED_HOSTS = []

# Application definition

INSTALLED_APPS = [

    'polls.apps.PollsConfig',

    'django.contrib.admin',

    'django.contrib.auth',

    'django.contrib.contenttypes',

    'django.contrib.sessions',

    'django.contrib.messages',

    'django.contrib.staticfiles',

]

MIDDLEWARE = [

    'django.middleware.security.SecurityMiddleware',

    'django.contrib.sessions.middleware.SessionMiddleware',

    'django.middleware.common.CommonMiddleware',

    'django.middleware.csrf.CsrfViewMiddleware',

    'django.contrib.auth.middleware.AuthenticationMiddleware',

    'django.contrib.messages.middleware.MessageMiddleware',

    'django.middleware.clickjacking.XFrameOptionsMiddleware',

]

ROOT_URLCONF = 'polls38.urls'

TEMPLATES = [

    {

        'BACKEND': 'django.template.backends.django.DjangoTemplates',

        'DIRS': [],

        'APP_DIRS': True,

        'OPTIONS': {

            'context_processors': [

                'django.template.context_processors.debug',

                'django.template.context_processors.request',

                'django.contrib.auth.context_processors.auth',

                'django.contrib.messages.context_processors.messages',

            ],

        },

    },

]

WSGI_APPLICATION = 'polls38.wsgi.application'

# Database

# https://docs.djangoproject.com/en/3.1/ref/settings/#databases

DATABASES = {

    'default': {

        'ENGINE': 'django.db.backends.sqlite3',

        'NAME': BASE_DIR / 'db.sqlite3',

    }

}

# Password validation

# https://docs.djangoproject.com/en/3.1/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [

    {

        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',

    },

    {

        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',

    },

    {

        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',

    },

    {

        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',

    },

]

# Internationalization

# https://docs.djangoproject.com/en/3.1/topics/i18n/

LANGUAGE_CODE = 'pt-br'

TIME_ZONE = 'America/Sao_Paulo'

USE_I18N = True

USE_L10N = True

USE_TZ = True

# Static files (CSS, JavaScript, Images)

# https://docs.djangoproject.com/en/3.1/howto/static-files/

STATIC_URL = '/static/'

To create de app "polls" I had to use the command:

django-admin startapp polls  polls38/polls (firstly I created the folder).

I was facing an error, when running "python manage.py runserver".

ERROR: module no found "polls".

I solved the problem, by adding at the manage.py the path to the app, as bellow (i do not believe that its the best solution)

def main():

    """Run administrative tasks."""

    sys.path.append('D:/linguagem/mooc/code/polls38/polls38')

    os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'polls38.settings')

    try:

        from django.core.management import execute_from_command_line

    except ImportError as exc:

        raise ImportError(

            "Couldn't import Django. Are you sure it's installed and "

            "available on your PYTHONPATH environment variable? Did you "

            "forget to activate a virtual environment?"

        ) from exc

    execute_from_command_line(sys.argv)

I was able to run the first and second part of the tutorial.

In the third part, after improving the polls/views, another problem showed-up.

And if I try to run, the follwing error occurs:

when I issue the command "python manage.py runserver"

(d:\conda_env\py38) D:\Linguagem\mooc\code\polls38>python manage.py runserver

D:\Linguagem\mooc\code\polls38

D:\Linguagem\mooc\code\polls38

Watching for file changes with StatReloader

Performing system checks...

Exception in thread django-main-thread:

Traceback (most recent call last):

  File "d:\conda_env\py38\lib\threading.py", line 932, in _bootstrap_inner

    self.run()

  File "d:\conda_env\py38\lib\threading.py", line 870, in run

    self._target(*self._args, **self._kwargs)

  File "d:\conda_env\py38\lib\site-packages\django\utils\autoreload.py", line 53, in wrapper

    fn(*args, **kwargs)

  File "d:\conda_env\py38\lib\site-packages\django\core\management\commands\runserver.py", line 118, in inner_run

    self.check(display_num_errors=True)

  File "d:\conda_env\py38\lib\site-packages\django\core\management\base.py", line 392, in check

    all_issues = checks.run_checks(

  File "d:\conda_env\py38\lib\site-packages\django\core\checks\registry.py", line 70, in run_checks

    new_errors = check(app_configs=app_configs, databases=databases)

  File "d:\conda_env\py38\lib\site-packages\django\core\checks\urls.py", line 13, in check_url_config

    return check_resolver(resolver)

  File "d:\conda_env\py38\lib\site-packages\django\core\checks\urls.py", line 23, in check_resolver

    return check_method()

  File "d:\conda_env\py38\lib\site-packages\django\urls\resolvers.py", line 408, in check

    for pattern in self.url_patterns:

  File "d:\conda_env\py38\lib\site-packages\django\utils\functional.py", line 48, in __get__

    res = instance.__dict__[self.name] = self.func(instance)

  File "d:\conda_env\py38\lib\site-packages\django\urls\resolvers.py", line 589, in url_patterns

    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)

  File "d:\conda_env\py38\lib\site-packages\django\utils\functional.py", line 48, in __get__

    res = instance.__dict__[self.name] = self.func(instance)

  File "d:\conda_env\py38\lib\site-packages\django\urls\resolvers.py", line 582, in urlconf_module

    return import_module(self.urlconf_name)

  File "d:\conda_env\py38\lib\importlib\__init__.py", line 127, in import_module

    return _bootstrap._gcd_import(name[level:], package, level)

  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import

  File "<frozen importlib._bootstrap>", line 991, in _find_and_load

  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked

  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked

  File "<frozen importlib._bootstrap_external>", line 783, in exec_module

  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed

  File "D:\Linguagem\mooc\code\polls38\polls38\urls.py", line 20, in <module>

    path('', include('polls38.polls.urls')),

  File "d:\conda_env\py38\lib\site-packages\django\urls\conf.py", line 34, in include

    urlconf_module = import_module(urlconf_module)

  File "d:\conda_env\py38\lib\importlib\__init__.py", line 127, in import_module

    return _bootstrap._gcd_import(name[level:], package, level)

  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import

  File "<frozen importlib._bootstrap>", line 991, in _find_and_load

  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked

  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked

  File "<frozen importlib._bootstrap_external>", line 783, in exec_module

  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed

  File "D:\Linguagem\mooc\code\polls38\polls38\polls\urls.py", line 3, in <module>

    from . import views

  File "D:\Linguagem\mooc\code\polls38\polls38\polls\views.py", line 7, in <module>

    from .models import Question

  File "D:\Linguagem\mooc\code\polls38\polls38\polls\models.py", line 6, in <module>

    class Question(models.Model):

  File "d:\conda_env\py38\lib\site-packages\django\db\models\base.py", line 113, in __new__

    raise RuntimeError(

RuntimeError: Model class polls38.polls.models.Question doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

Any help on how to fix?

tks a lot!!

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