ObjectDoesNotExist 没有捕捉到 DoesNotExist 异常

Question

我正在尝试捕获 DoesNotExist 异常，并且检查引发异常的代码很困难。我无法到达在 pdb 中引发它的行，并且在调试跟踪中没有关于什么对象引发异常的信息，因为它包含在实例变量下，因此 django 跟踪不显示它的值是什么。

我已经阅读了https://docs.djangoproject.com/en/1.11/ref/exceptions/#objectdoesnotexist 的文档和Catching Any DoesNotExist Error 的这个问题。这两个都表明要捕获任何 DoesNotExist 异常，只需导入 ObjectDoesNotExist 并涵盖所有这些异常。我的情况不是这样。我的 except ObjectDoesNotExist 块中没有捕获异常。

代码：

from django.core.exceptions import ObjectDoesNotExist

def check_permission(user):
    """function checks whether the user is in the list of allowed groups"""
    for option in ALLOWED: # list of groups, constant
        try:
            if user.groups.get().name == option:
                return True
        except ObjectDoesNotExist:
            pass
        else:
            pass
    return False

跟踪显示：

File 
".../lib/python3.6/site-packages/django/db/models/query.py", line 379, in get self.model._meta.object_name

django.contrib.auth.models.DoesNotExist: Group matching query does not exist.

从我的代码行中抛出的内容：

if user.groups.get().name == option

尝试访问 django.contrib.auth.models.DoesNotExist 只会返回一个

AttributeError: model 'django.contrib.auth.models' has no attribute 'DoesNotExist'

我如何捕捉到这个？有时用户不会有任何组，即使网站设计为永远不会发生这种情况，但这里有易破解的代码仍然让我感到紧张。

编辑：python 3.6.2 django 1.11

完整的跟踪：

Traceback (most recent call last):
  File ".../lib/python3.6/site-packages/django/core/handlers/exception.py", line 41, in inner
response = get_response(request)
  File ".../lib/python3.6/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response
response = self._get_response(request)
  File ".../lib/python3.6/site-packages/django/core/handlers/base.py", line 187, in _get_response
response = self.process_exception_by_middleware(e, request)
  File ".../lib/python3.6/site-packages/django/core/handlers/base.py", line 185, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File ".../lib/python3.6/site-packages/django/contrib/auth/decorators.py", line 23, in _wrapped_view
return view_func(request, *args, **kwargs)
  File ".../lib/python3.6/site-packages/django/views/generic/base.py", line 68, in view
return self.dispatch(request, *args, **kwargs)
  File ".../lib/python3.6/site-packages/django/views/generic/base.py", line 88, in dispatch
return handler(request, *args, **kwargs)
  File "/Users/Mark/Desktop/Professional/FSC/water/WATER/sharedClasses.py", line 116, in get
return self.permission_denied_page(request, plans)
  File "/Users/Mark/Desktop/Professional/FSC/water/WATER/sharedClasses.py", line 68, in permission_denied_page
their_acccount = user.groups.get().name
  File ".../lib/python3.6/site-packages/django/db/models/manager.py", line 85, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
  File ".../lib/python3.6/site-packages/django/db/models/query.py", line 379, in get
self.model._meta.object_name
django.contrib.auth.models.DoesNotExist: Group matching query does not exist.

Answer 1

你应该像这样导入 Group 和 catch：'

from django.contrib.auth.models import Group

try:
    // your code
except Group.DoesNotExist:
   // to handle

顺便说一句，你为什么不以更优化的方式编写你的方法：

def check_permission(user):
   """return true if the user is in options, false if not"""
   if user.groups.filter(name__in=ALLOWED).exists():
      return True
   else:
      return False