python - 为什么在 Django 视图中无法捕获异常以及如何调试

Question

我对这个删除视图很满意：

def price_unit_delete(request, pk):
    pu = PriceUnit.objects.get(pk=pk)
    template = 'includes/modal/modal_form.html'
    if request.POST:
        pu.delete()
        template = 'dashboard_staff/settings/includes/priceunits.html'
    ctx = {'action': reverse("dashboard_staff:settings_delete_priceunit", args=(pu.pk, )),
           'title': 'do you really want to delete me ?',
           'form': PriceUnitDeleteForm(),
           'priceunits': PriceUnit.objects.all()}
    return TemplateResponse(request, template, ctx)

当一个项目在其他地方作为外键引用时，它会失败。try我想用一个块来捕捉这个完整性错误（首先由 psycopg2 提出，其次由 django.db 本身提出） 。

确实，您可以在 python 控制台中执行以下操作：

# in case of ```o``` being referenced somewhere else, returns False

def delete(o):
    try:
        o.delete()
    except:
        return False

我天真地认为在这样的视图中包含这样一个块：

   if request.POST:
        try:
            pu.delete()
        except:
            return JsonResponse({'data': _(
                "You can't delete this object as it is used somewhere else."
            )}, status=400)

但在这种情况下，异常不会被捕获。我也将此视图写为 CBV，它也未能捕获异常。

我在另一个项目中尝试了这段代码，它可以工作。

为什么这在完整性异常的情况下不起作用？我该如何调试它？

这是我要捕获的异常的回溯：

  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/db/backends/base/base.py", line 240, in _commit
    return self.connection.commit()
psycopg2.IntegrityError: update or delete on table "prices_priceunit" violates foreign key constraint "prices_prestationtyp_default_price_unit_i_c6ec94f9_fk_prices_pr" on table "prices_prestationtype"
DETAIL:  Key (id)=(1) is still referenced from table "prices_prestationtype".


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python3.7/contextlib.py", line 74, in inner
    return func(*args, **kwds)
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/db/transaction.py", line 240, in __exit__
    connection.commit()
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/db/backends/base/base.py", line 262, in commit
    self._commit()
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/db/backends/base/base.py", line 240, in _commit
    return self.connection.commit()
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/db/utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/home/emilio/.virtualenvs/rdt_2.0/lib/python3.7/site-packages/django/db/backends/base/base.py", line 240, in _commit
    return self.connection.commit()
django.db.utils.IntegrityError: update or delete on table "prices_priceunit" violates foreign key constraint "prices_prestationtyp_default_price_unit_i_c6ec94f9_fk_prices_pr" on table "prices_prestationtype"
DETAIL:  Key (id)=(1) is still referenced from table "prices_prestationtype".

标签： pythondjangoexceptionerror-handling