Django .get() 返回一个元组而不是对象

Question

我有一个简单的函数，如下所示：

parent_key = SeoKeys.objects.get(view_id=view_id, key_nbr=key_nbr)
    if parent_key.status != 'active':
        parent_key.status = status
        parent_key.save()

    metrics, created = SeoMetrics.objects.get_or_create(
                                                        seo_url = url_sent,
                                                        date = date,
                                                        parent_key = parent_key,
                                                        defaults = {
                                                                'parent_key':parent_key,
                                                                'seo_url': url_sent,
                                                                'url_found':url_found,
                                                                'position':position,
                                                                }
                                                        )

现在理论上这应该可以工作，但是我收到以下错误：

ValueError: Cannot assign "(<SeoKeys: SeoKeys object>,)": "SeoMetrics.parent_key" must be a "SeoKeys" instance.

这是因为它是一个元组。如果我这样做 'parent_key':parent_key[0] 它会很好地保存它。然而，这似乎是一个相当黑客的解决方案，我想了解为什么会发生这种情况。有什么想法吗？

我的模型看起来像这样：

class SeoMetrics(models.Model):
    parent_key = models.ForeignKey('SeoKeys', on_delete=models.CASCADE)

编辑： 添加了完整的错误：

Internal Server Error: /hook/
Traceback (most recent call last):
  File "/Users/Costantin/GDrive/Analytic.me/dev/venv/lib/python3.5/site-packages/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "/Users/Costantin/GDrive/Analytic.me/dev/venv/lib/python3.5/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/Users/Costantin/GDrive/Analytic.me/dev/venv/lib/python3.5/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/Costantin/GDrive/Analytic.me/dev/venv/lib/python3.5/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
  File "/Users/Costantin/GDrive/Analytic.me/dev/backend/apps/seo_app/views.py", line 152, in webhook
    metrics.parent_key = parent,
  File "/Users/Costantin/GDrive/Analytic.me/dev/venv/lib/python3.5/site-packages/django/db/models/fields/related_descriptors.py", line 216, in __set__
    self.field.remote_field.model._meta.object_name,
ValueError: Cannot assign "(<SeoKeys: SeoKeys object>,)": "SeoMetrics.parent_key" must be a "SeoKeys" instance.

Answer 1

 File "/Users/Costantin/GDrive/Analytic.me/dev/backend/apps/seo_app/views.py", line 152, in webhook
   metrics.parent_key = parent,

这段代码正在创建一个元组。删除行尾的逗号。