Django 소스 읽기 (2) INSTALLEDAPPS 로드 프로세스

# django\core\management\__init__.py
def execute(self):
    ...
    if settings.configured:
        # Start the auto-reloading dev server even if the code is broken.
        # The hardcoded condition is a code smell but we can't rely on a
        # flag on the command class because we haven't located it yet.
        if subcommand == 'runserver' and '--noreload' not in self.argv:
            try:
                autoreload.check_errors(django.setup)()
            except Exception:
                # The exception will be raised later in the child process
                # started by the autoreloader. Pretend it didn't happen by
                # loading an empty list of applications.
                apps.all_models = defaultdict(OrderedDict)
                apps.app_configs = OrderedDict()
                apps.apps_ready = apps.models_ready = apps.ready = True

                # Remove options not compatible with the built-in runserver
                # (e.g. options for the contrib.staticfiles' runserver).
                # Changes here require manually testing as described in
                # #27522.
                _parser = self.fetch_command('runserver').create_parser('django', 'runserver')
                _options, _args = _parser.parse_known_args(self.argv[2:])
                for _arg in _args:
                    self.argv.remove(_arg)

        # In all other cases, django.setup() is required to succeed.
        else:
            django.setup()
    ...

def setup(set_prefix=True):
    """
    Configure the settings (this happens as a side effect of accessing the
    first setting), configure logging and populate the app registry.
    Set the thread-local urlresolvers script prefix if `set_prefix` is True.
    """
    ...
    configure_logging(settings.LOGGING_CONFIG, settings.LOGGING)
    if set_prefix:
        set_script_prefix(
            '/' if settings.FORCE_SCRIPT_NAME is None else settings.FORCE_SCRIPT_NAME
        )
    apps.populate(settings.INSTALLED_APPS)

    def populate(self, installed_apps=None):
        # populate() might be called by two threads in parallel on servers
        # that create threads before initializing the WSGI callable.
        with self._lock:
            ...
            for entry in installed_apps:
                if isinstance(entry, AppConfig):
                    app_config = entry
                else:
                    app_config = AppConfig.create(entry)
                ...
                self.app_configs[app_config.label] = app_config
                app_config.apps = self
            ...

        try:
            app_name = cls.name
        except AttributeError:
            raise ImproperlyConfigured(
                "'%s' must supply a name attribute." % entry)

        # Ensure app_name points to a valid module.
        try:
            app_module = import_module(app_name)

            # Phase 2: import models modules.
            for app_config in self.app_configs.values():
            #       ，      app  
                app_config.import_models()

            self.clear_cache()

            self.models_ready = True

            # Phase 3: run ready() methods of app configs.
            for app_config in self.get_app_configs():
            #        
                app_config.ready()

            self.ready = True
            self.ready_event.set()
            
#   self.get_app_configs()
odict_values([<AdminConfig: admin>, 
<AuthConfig: auth>, 
<ContentTypesConfig: contenttypes>, 
<SessionsConfig: sessions>, 
<MessagesConfig: messages>,
...
<AppConfig: pure_pagination>])

#   import_models      self.models_module
<module 'django.contrib.admin.models' from 'C:\\mooc_project\\lib\\site-packages\\django\\contrib\\admin\\models.py'>
<module 'django.contrib.auth.models' from 'C:\\mooc_project\\lib\\site-packages\\django\\contrib\\auth\\models.py'>
<module 'django.contrib.contenttypes.models' from 'C:\\mooc_project\\lib\\site-packages\\django\\contrib\\contenttypes\\models.py'>
<module 'django.contrib.sessions.models' from 'C:\\mooc_project\\lib\\site-packages\\django\\contrib\\sessions\\models.py'>
#         ，self.models                    。