[docs] class AppConfig : """Class representing a Django application and its configuration.""" def __init__ ( self , app_name , app_module ): # Full Python path to the application e.g. 'django.contrib.admin'. self . name = app_name # Root module for the application e.g. <module 'django.contrib.admin' # from 'django/contrib/admin/__init__.py'>. self . module = app_module # Reference to the Apps registry that holds this AppConfig. Set by the # registry when it registers the AppConfig instance. self . apps = None # The following attributes could be defined at the class level in a # subclass, hence the test-and-set pattern. # Last component of the Python path to the application e.g. 'admin'. # This value must be unique across a Django project. if not hasattr ( self , "label" ): self . label = app_name . rpartition ( "." )[ 2 ] if not self . label . isidentifier (): raise ImproperlyConfigured ( "The app label ' %s ' is not a valid Python identifier." % self . label # Human-readable name for the application e.g. "Admin". if not hasattr ( self , "verbose_name" ): self . verbose_name = self . label . title () # Filesystem path to the application directory e.g. # '/path/to/django/contrib/admin'. if not hasattr ( self , "path" ): self . path = self . _path_from_module ( app_module ) # Module containing models e.g. <module 'django.contrib.admin.models' # from 'django/contrib/admin/models.py'>. Set by import_models(). # None if the application doesn't have a models module. self . models_module = None # Mapping of lowercase model names to model classes. Initially set to # None to prevent accidental access before import_models() runs. self . models = None def __repr__ ( self ): return "< %s : %s >" % ( self . __class__ . __name__ , self . label ) @cached_property def default_auto_field ( self ): from django.conf import settings return settings . DEFAULT_AUTO_FIELD @property def _is_default_auto_field_overridden ( self ): return self . __class__ . default_auto_field is not AppConfig . default_auto_field def _path_from_module ( self , module ): """Attempt to determine app's filesystem path from its module.""" # See #21874 for extended discussion of the behavior of this method in # various cases. # Convert to list because __path__ may not support indexing. paths = list ( getattr ( module , "__path__" , [])) if len ( paths ) != 1 : filename = getattr ( module , "__file__" , None ) if filename is not None : paths = [ os . path . dirname ( filename )] else : # For unknown reasons, sometimes the list returned by __path__ # contains duplicates that must be removed (#25246). paths = list ( set ( paths )) if len ( paths ) > 1 : raise ImproperlyConfigured ( "The app module %r has multiple filesystem locations ( %r ); " "you must configure this app with an AppConfig subclass " "with a 'path' class attribute." % ( module , paths ) elif not paths : raise ImproperlyConfigured ( "The app module %r has no filesystem location, " "you must configure this app with an AppConfig subclass " "with a 'path' class attribute." % module return paths [ 0 ] @classmethod def create ( cls , entry ): Factory that creates an app config from an entry in INSTALLED_APPS. # create() eventually returns app_config_class(app_name, app_module). app_config_class = None app_config_name = None app_name = None app_module = None # If import_module succeeds, entry points to the app module. try : app_module = import_module ( entry ) except Exception : else : # If app_module has an apps submodule that defines a single # AppConfig subclass, use it automatically. # To prevent this, an AppConfig subclass can declare a class # variable default = False. # If the apps module defines more than one AppConfig subclass, # the default one can declare default = True. if module_has_submodule ( app_module , APPS_MODULE_NAME ): mod_path = " %s . %s " % ( entry , APPS_MODULE_NAME ) mod = import_module ( mod_path ) # Check if there's exactly one AppConfig candidate, # excluding those that explicitly define default = False. app_configs = [ ( name , candidate ) for name , candidate in inspect . getmembers ( mod , inspect . isclass ) if ( issubclass ( candidate , cls ) and candidate is not cls and getattr ( candidate , "default" , True ) if len ( app_configs ) == 1 : app_config_class = app_configs [ 0 ][ 1 ] app_config_name = " %s . %s " % ( mod_path , app_configs [ 0 ][ 0 ]) else : # Check if there's exactly one AppConfig subclass, # among those that explicitly define default = True. app_configs = [ ( name , candidate ) for name , candidate in app_configs if getattr ( candidate , "default" , False ) if len ( app_configs ) > 1 : candidates = [ repr ( name ) for name , _ in app_configs ] raise RuntimeError ( " %r declares more than one default AppConfig: " " %s ." % ( mod_path , ", " . join ( candidates )) elif len ( app_configs ) == 1 : app_config_class = app_configs [ 0 ][ 1 ] app_config_name = " %s . %s " % ( mod_path , app_configs [ 0 ][ 0 ]) # If app_module specifies a default_app_config, follow the link. # default_app_config is deprecated, but still takes over the # automatic detection for backwards compatibility during the # deprecation period. try : new_entry = app_module . default_app_config except AttributeError : # Use the default app config class if we didn't find anything. if app_config_class is None : app_config_class = cls app_name = entry else : message = " %r defines default_app_config = %r . " % ( entry , new_entry ) if new_entry == app_config_name : message += ( "Django now detects this configuration automatically. " "You can remove default_app_config." else : message += ( "However, Django's automatic detection %s . You should " "move the default config class to the apps submodule " "of your application and, if this module defines " "several config classes, mark the default one with " "default = True." "picked another configuration, %r " % app_config_name if app_config_name else "did not find this configuration" warnings . warn ( message , RemovedInDjango41Warning , stacklevel = 2 ) entry = new_entry app_config_class = None # If import_string succeeds, entry is an app config class. if app_config_class is None : try : app_config_class = import_string ( entry ) except Exception : # If both import_module and import_string failed, it means that entry # doesn't have a valid value. if app_module is None and app_config_class is None : # If the last component of entry starts with an uppercase letter, # then it was likely intended to be an app config class; if not, # an app module. Provide a nice error message in both cases. mod_path , _ , cls_name = entry . rpartition ( "." ) if mod_path and cls_name [ 0 ] . isupper (): # We could simply re-trigger the string import exception, but # we're going the extra mile and providing a better error # message for typos in INSTALLED_APPS. # This may raise ImportError, which is the best exception # possible if the module at mod_path cannot be imported. mod = import_module ( mod_path ) candidates = [ repr ( name ) for name , candidate in inspect . getmembers ( mod , inspect . isclass ) if issubclass ( candidate , cls ) and candidate is not cls msg = "Module ' %s ' does not contain a ' %s ' class." % ( mod_path , cls_name , if candidates : msg += " Choices are: %s ." % ", " . join ( candidates ) raise ImportError ( msg ) else : # Re-trigger the module import exception. import_module ( entry ) # Check for obvious errors. (This check prevents duck typing, but # it could be removed if it became a problem in practice.) if not issubclass ( app_config_class , AppConfig ): raise ImproperlyConfigured ( "' %s ' isn't a subclass of AppConfig." % entry ) # Obtain app name here rather than in AppClass.__init__ to keep # all error checking for entries in INSTALLED_APPS in one place. if app_name is None : try : app_name = app_config_class . 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 ) except ImportError : raise ImproperlyConfigured ( "Cannot import ' %s '. Check that ' %s . %s .name' is correct." app_name , app_config_class . __module__ , app_config_class . __qualname__ , # Entry is a path to an app config class. return app_config_class ( app_name , app_module )