有没有办法绕过“NoneType”对象没有属性“DoesNotExist”

debugcn 发表于 Dev

9分钟

我试图呈现相同的页面“计费”，但根据用户是否有活动订阅而具有不同的变量。问题是当我尝试例外时，我得到 'NoneType' 对象没有属性 'DoesNotExist'。

如果成员资格为 False，我曾尝试使用：返回重定向但没有成功。

@login_required(login_url="/login")
def billing(request):
    membership = False
    cancel_at_period_end = False
    user = request.user
    pay = payment.objects.filter(user=user).last()
    if request.method == 'POST':
       stripe.api_key = settings.STRIPE_SECRET_KEY
       #attempting cancelling  subscription
       subscription = stripe.Subscription.retrieve(pay.stripe_subscription_id)
       subscription.cancel_at_period_end = True
       pay.cancel_at_period_end = True
       cancel_at_period_end = True
       pay.paid  = False
       subscription.save()
       pay.save()
       messages.success(
            request, "Thankyou, for using our services Your membership will run to the end of your billing cycle.")
    else:
        try:
            if pay.paid:
                membership = True
            if pay.cancel_at_period_end:
                cancel_at_period_end = True
        except pay.DoesNotExist:
            membership = False
    return render(request, 'billing.html',  {'membership': membership, 'pay': pay,  'cancel_at_period_end': cancel_at_period_end})

Traceback:

File "/Users/iamsuccessful/totdapp-2/totdapp/views.py" in billing
  94.             if pay.paid:

During handling of the above exception ('NoneType' object has no attribute 'paid'), another exception occurred:

File "/Users/iamsuccessful/totdapp/totdenv/lib/python3.7/site-packages/django/core/handlers/exception.py" in inner
  34.             response = get_response(request)

File "/Users/iamsuccessful/totdapp/totdenv/lib/python3.7/site-packages/django/core/handlers/base.py" in _get_response
  115.                 response = self.process_exception_by_middleware(e, request)

File "/Users/iamsuccessful/totdapp/totdenv/lib/python3.7/site-packages/django/core/handlers/base.py" in _get_response
  113.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/Users/iamsuccessful/totdapp/totdenv/lib/python3.7/site-packages/django/contrib/auth/decorators.py" in _wrapped_view
  21.                 return view_func(request, *args, **kwargs)

File "/Users/iamsuccessful/totdapp-2/totdapp/views.py" in billing
  98.         except pay.DoesNotExist or AttributeError:

Exception Type: AttributeError at /billing/
Exception Value: 'NoneType' object has no attribute 'DoesNotExist'

如果用户没有活动订阅，我希望重定向到 ('')（主页）。

阿拉斯代尔

从模型访问异常，例如payment.DoesNotExist。

在 Python/Django 中，您应该将模型大写，例如class Payment(models.Model):. 使用小写payment会使您的代码难以阅读，并且更容易出错。

在您的回溯中，您有：

except pay.DoesNotExist or AttributeError:

这是不正确的，您应该使用要捕获的异常元组，例如：

except (payment.DoesNotExist, AttributeError):

payment.DoesNotExist or AttributeError将简化为payment.DoesNotExist，因此您永远不会遇到AttributeError.

最后，DoesNotExist当您执行Payment.objects.get(...). 你的线pay.paid永远不会提高DoesNotExist，但它可以提高AttributeError的时候pay是None。您可以将代码简化为：

try:
    if pay.paid:
        membership = True
    if pay.cancel_at_period_end:
        cancel_at_period_end = True
except AttributeError:
    membership = False

但是，如果你检查是否代码可能会更清晰pay的None。

if pay is not None:
    if pay.paid:
        membership = True
    if pay.cancel_at_period_end:
        cancel_at_period_end = True
else:
    membership = False

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