def load_class(class_path, setting_name=None):
    """
    Loads a class given a class_path. The setting value may be a string or a
    tuple.

    The setting_name parameter is only there for pretty error output, and
    therefore is optional
    """
    if not isinstance(class_path, six.string_types):
        try:
            class_path, app_label = class_path
        except:
            if setting_name:
                raise exceptions.ImproperlyConfigured(CLASS_PATH_ERROR % (
                    setting_name, setting_name))
            else:
                raise exceptions.ImproperlyConfigured(CLASS_PATH_ERROR % (
                    'this setting', 'It'))

    try:
        class_module, class_name = class_path.rsplit('.', 1)
    except __HOLE__:
        if setting_name:
            txt = '%s isn\'t a valid module. Check your %s setting' % (
                class_path, setting_name)
        else:
            txt = '%s isn\'t a valid module.' % class_path
        raise exceptions.ImproperlyConfigured(txt)

    try:
        mod = import_module(class_module)
    except ImportError as e:
        if setting_name:
            txt = 'Error importing backend %s: "%s". Check your %s setting' % (
                class_module, e, setting_name)
        else:
            txt = 'Error importing backend %s: "%s".' % (class_module, e)

        raise exceptions.ImproperlyConfigured(txt)

    try:
        clazz = getattr(mod, class_name)
    except AttributeError:
        if setting_name:
            txt = ('Backend module "%s" does not define a "%s" class. Check'
                   ' your %s setting' % (class_module, class_name,
                                         setting_name))
        else:
            txt = 'Backend module "%s" does not define a "%s" class.' % (
                class_module, class_name)
        raise exceptions.ImproperlyConfigured(txt)
    return clazz
dataset/ETHPy150Open ulule/django-courriers/courriers/utils.py/load_class