Django queryset values_list是否返回列表对象？ [英] Does Django queryset values_list return a list object?

问题描述

我有一个Django应用，用户可以在其中发布照片，并在照片下方发表其他评论。

留下评论时，我需要通知：

1. 其他人谁在此线程中撰写


2. 照片的所有者，以防不属于（1）

对于（1），我这样做：

  #I切成25分，因为我任意认为超出此范围的任何人不相关的。 
 all_commenter_ids = PhotoComment.objects.filter（which_photo = which_photo）.order_by（'-id'）。values_list（'submitted_by'，flat = True）[：25] 
  

接下来，对于（2），我尝试：

  all_relevant_ids = all_commenter_ids.append（which_photo.owner_id）
 all_relevant_ids = list（set（all_relevant_ids））
  

我最终得到一个错误：

'ValuesListQuerySet'对象没有属性'append'

我发现这很奇怪，因为我正在提取 values_list 。

不是列表对象，在这种情况下，属性不应添加场景？请解释问题所在，并提出其他建议。

解决方案

values_list 方法返回 ValuesListQuerySet 。这意味着它具有查询集的优点。例如，它是惰性的，因此切片时仅从数据库中获取前25个元素。

要将其转换为列表，请使用 list（）。

  all_commenter_ids = PhotoComment.objects.filter（which_photo = which_photo）.order_by （'-id'）。values_list（'submitted_by'，flat = True）[：25] 
 all_commenter_ids = list（all_commenter_ids）
  

您也许可以从 User 模型启动查询集，而不必使用 values_list 。您尚未显示模型，因此下面的代码是一个猜测：

from django.db.models import Q

评论者= User.objects.filter（Q（id = which_photo.owner_id）| Q（photocomment = which_photo））


I have a Django app where users post photos, and other leave comments under the photos.

When a comment is left, I need to notify:

1. Everyone else who wrote in this thread
2. The owner of the photo, in case they're not included in (1)

For (1), I do:

#I slice by 25 because I arbitrarily deem anyone beyond that irrelevant. 
all_commenter_ids = PhotoComment.objects.filter(which_photo=which_photo).order_by('-id').values_list('submitted_by', flat=True)[:25]

Next, for (2), I try:

all_relevant_ids = all_commenter_ids.append(which_photo.owner_id)
all_relevant_ids = list(set(all_relevant_ids))

I end up with an error:

'ValuesListQuerySet' object has no attribute 'append'

I find this strange, because I'm extracting a values_list.

Isn't that a list object, and in that case, shouldn't the attribute append work in this scenario? Please explain what's wrong, and suggest alternatives.

解决方案

The values_list method returns a ValuesListQuerySet. This means it has the advantages of a queryset. For example it is lazy, so you only fetch the first 25 elements from the database when you slice it.

To convert it to a list, use list().

all_commenter_ids = PhotoComment.objects.filter(which_photo=which_photo).order_by('-id').values_list('submitted_by', flat=True)[:25]
all_commenter_ids = list(all_commenter_ids)

You might be able to start the queryset from your User model instead of using values_list. You haven't shown your models, so the following code is a guess:

from django.db.models import Q

commenters = User.objects.filter(Q(id=which_photo.owner_id)|Q(photocomment=which_photo))

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