I'm fairly new to programming and I was learning Python by following the textbook No Starch Python. There is a chapter on Django and I followed the steps of the textbook. However, when I run the program:

from django.db import models

class Topic(models.Model):
    """A topic the user is learning about"""
    text = models.CharField(max_length=200)
    date_added = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        """Return a string representation of the model."""
        return self.text

I will get this error message:

Traceback (most recent call last):
  File "/Users/admin/learning_log2/learning_logs/models.py", line 4, in <module>
    class Topic(models.Model):
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/django/db/models/base.py", line 127, in __new__
    app_config = apps.get_containing_app_config(module)
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/django/apps/registry.py", line 260, in get_containing_app_config
    self.check_apps_ready()
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/django/apps/registry.py", line 137, in check_apps_ready
    settings.INSTALLED_APPS
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/django/conf/__init__.py", line 92, in __getattr__
    self._setup(name)
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/django/conf/__init__.py", line 72, in _setup
    raise ImproperlyConfigured(
django.core.exceptions.ImproperlyConfigured: Requested setting INSTALLED_APPS, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.

Here's the settings module:

"""
Django settings for learning_log project.

Generated by 'django-admin startproject' using Django 4.1.5.

For more information on this file, see
https://docs.djangoproject.com/en/4.1/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/4.1/ref/settings/
"""

from pathlib import Path

# Build paths inside the project like this: BASE_DIR / 'subdir'.
BASE_DIR = Path(__file__).resolve().parent.parent


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/4.1/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = 'django-insecure-y8l9_wqzuq6#q@_0=f*$4-k_^o_enm3mmq oe!*f*i-ktah(9w'

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

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = [
    '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 = 'learning_log.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 = 'learning_log.wsgi.application'


# Database
# https://docs.djangoproject.com/en/4.1/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR / 'db.sqlite3',
    }
}


# Password validation
# https://docs.djangoproject.com/en/4.1/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/4.1/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/4.1/howto/static-files/

STATIC_URL = 'static/'

# Default primary key field type
# https://docs.djangoproject.com/en/4.1/ref/settings/#default-auto-field

DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'

Can anyone tell me why it is the case and what can I do? Thank you very much. P.S. I know there is already a post on this but I tried what was written without any results. Also, I'm on macOS High Sierra version 10.13.6 if this information is relevant.

I tried whatever I could find on the internet but nothing seems to work. I don't even have a fundamental understanding of the problem.

CodePudding user response：

You need to specify the django app name in the settings.py file before start using it.

You were created a Django Application before creating this model 'Topic' with a command

python manage.py startapp core 

you need to provide the appname (in the above case it is 'core') under settings.py file in the array like bellow

INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'core' #new app name

]

CodePudding user response：

I don't even have a fundamental understanding of the problem

Since you're defining a model, Django assumes that you might want to store instances of that model in a database.

To do that, Django needs to know the connection details for your chosen database, and those details are stored in the settings.py module.

You didn't tell Django where to find that module.