循环/更改对象列表中某些对象的最佳方法

Question

假设我有这个代码：

# Get 30 threads
threads = Thread.objects.all()[:30]
threads_id = [o.pk for o in threads]
# Extra info about threads that the user have visited
visited_threads = VisitedThread.objects.filter(pk__in=threads_id, user=request.user)

# I want to loop the visited_threads and add info to thread in threads with new info
for visited_thread in visited_threads:
    # Here I want to add things to thread (visited_thread.thread), something like:
    # thread.has_unread_post = thread.post_count > visited_thread.post_count

如何向threads列表中的线程添加信息，如代码示例中的某些内容？我不想更新数据库，只是在向用户显示数据之前对其进行操作。你知道吗

Answer 1

您展示的示例代码很好，至少在一般意义上是这样的。一旦您开始迭代queryset，Django将创建内存中的模型实例，并且您可以像任何其他Python对象一样向内存中的版本添加属性。你知道吗

要基于第二个Q编辑第一个Q中的线程，请执行以下操作：

threads = Thread.objects.all()[:30]
threads_by_pk = dict((t.pk, t) for t in threads)
# Extra info about threads that the user have visited
visited_threads = VisitedThread.objects.filter(pk__in=threads_by_pk.keys(), user=request.user)

# I want to loop the visited_threads and add info to thread in threads with new info
for visited_thread in visited_threads:
    thread = threads_by_pk[visited_thread.pk]
    thread.has_unread_post = thread.post_count > visited_thread.post_count