def by_name(backend=None, loader=None, extension_namespace=u'celery.result_backends'):
 backend = (backend or u'disabled')
 loader = (loader or current_app.loader)
 aliases = dict(BACKEND_ALIASES, **loader.override_backends)
 aliases.update((load_extension_class_names(extension_namespace) or {}))
 try:
  cls = symbol_by_name(backend, aliases)
 except ValueError as exc:
  reraise(ImproperlyConfigured, ImproperlyConfigured(UNKNOWN_BACKEND.strip().format(backend, exc)), sys.exc_info()[2])
 if isinstance(cls, types.ModuleType):
  raise ImproperlyConfigured(UNKNOWN_BACKEND.strip().format(backend, u'is a Python module, not a backend class.'))
 return cls

def by_name ( backend = None , loader = None , extension_namespace = u'celery.result_backends' ) : backend = ( backend or u'disabled' ) loader = ( loader or current_app . loader ) aliases = dict ( BACKEND_ALIASES , ** loader . override_backends ) aliases . update ( ( load_extension_class_names ( extension_namespace ) or { } ) ) try : cls = symbol_by_name ( backend , aliases ) except ValueError as exc : reraise ( ImproperlyConfigured , ImproperlyConfigured ( UNKNOWN_BACKEND . strip ( ) . format ( backend , exc ) ) , sys . exc_info ( ) [ 2 ] ) if isinstance ( cls , types . ModuleType ) : raise ImproperlyConfigured ( UNKNOWN_BACKEND . strip ( ) . format ( backend , u'is a Python module, not a backend class.' ) ) return cls
get backend class by name/alias .