Django2.0异常：Specifying a namespace in include() without providing an app_name is not supported.

我的代码为：

urlpatterns = [url(r'^admin/', admin.site.urls),url(r'^polls/', include('polls.urls', namespace="polls")),
]

具体的错误为：

'Specifying a namespace in include() without providing an app_name is not supported. Set the app_name attribute in the included module, or pass a 2-tuple containing the list of patterns and app_name instead.'

查找错误出处，为conf.py文件

源代码如下：

def include(arg, namespace=None):app_name = Noneif isinstance(arg, tuple):# Callable returning a namespace hint.try:urlconf_module, app_name = argexcept ValueError:if namespace:raise ImproperlyConfigured('Cannot override the namespace for a dynamic module that ''provides a namespace.')raise ImproperlyConfigured('Passing a %d-tuple to include() is not supported. Pass a ''2-tuple containing the list of patterns and app_name, and ''provide the namespace argument to include() instead.' % len(arg))else:# No namespace hint - use manually provided namespace.urlconf_module = argif isinstance(urlconf_module, str):urlconf_module = import_module(urlconf_module)patterns = getattr(urlconf_module, 'urlpatterns', urlconf_module)app_name = getattr(urlconf_module, 'app_name', app_name)if namespace and not app_name:raise ImproperlyConfigured('Specifying a namespace in include() without providing an app_name ''is not supported. Set the app_name attribute in the included ''module, or pass a 2-tuple containing the list of patterns and ''app_name instead.',)namespace = namespace or app_name# Make sure the patterns can be iterated through (without this, some# testcases will break).if isinstance(patterns, (list, tuple)):for url_pattern in patterns:pattern = getattr(url_pattern, 'pattern', None)if isinstance(pattern, LocalePrefixPattern):raise ImproperlyConfigured('Using i18n_patterns in an included URLconf is not allowed.')return (urlconf_module, app_name, namespace)

从include()函数可以看出来，这个函数有两个参数，一个arg，一个namespace，我在代码中也是两个参数，但是异常中提示了，没有提供app_name,还提示需要传入一个两元元组，从第六行代码

urlconf_module, app_name = arg

可以看出来，arg就是那个元组，且给app_name赋值了，所以我们这里修改代码为：

urlpatterns = [url(r'^admin/', admin.site.urls),url(r'^polls/', include(('polls.urls', "polls"), namespace="polls")),
]

问题解决。