Django错误does not appear to have any patterns in it. If you see valid patterns in the file then the i

Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/django/urls/resolvers.py", line 581, in url_patterns
    iter(patterns)
TypeError: 'module' object is not iterable

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/local/lib/python3.5/dist-packages/django/utils/autoreload.py", line 54, in wrapper
    fn(*args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/commands/runserver.py", line 117, in inner_run
    self.check(display_num_errors=True)
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 390, in check
    include_deployment_checks=include_deployment_checks,
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 377, in _run_checks
    return checks.run_checks(**kwargs)
  File "/usr/local/lib/python3.5/dist-packages/django/core/checks/registry.py", line 72, in run_checks
    new_errors = check(app_configs=app_configs)
  File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 13, in check_url_config
    return check_resolver(resolver)
  File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 23, in check_resolver
    return check_method()
  File "/usr/local/lib/python3.5/dist-packages/django/urls/resolvers.py", line 398, in check
    for pattern in self.url_patterns:
  File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/usr/local/lib/python3.5/dist-packages/django/urls/resolvers.py", line 588, in url_patterns
    raise ImproperlyConfigured(msg.format(name=self.urlconf_name))
django.core.exceptions.ImproperlyConfigured: The included URLconf 'Web_Django.urls' does not appear to have any patterns in it. If you see valid patterns in the file then the issue is probably caused by a circular import.

在运行python3 manage.py runserver 0.0.0.0:8000的时候发生了以上的错误，百度了大半个小时，最后找到原因：

在urls.py中的一条语句：

 path('RCodePage/', learn_views.R_code_page,name='R_code_page'),

而views.py中我把函数R_code_page给删掉了，因此导致他找不到这个函数而报错。