Django values_list vs values

问题:

In Django, what's the difference between the following two:

Article.objects.values_list('comment_id', flat=True).distinct()

vs

Article.objects.values('comment_id').distinct()

My goal is to get a list of unique comment ids under each Article. I've read the documentation (and in fact have used both approaches). The results overtly seem similar.

回答1:

The values() method returns a QuerySet containing dictionaries:

<QuerySet [{'comment_id': 1}, {'comment_id': 2}]>

The values_list() method returns a QuerySet containing tuples:

<QuerySet [(1,), (2,)]>

If you are using values_list() with a single field, you can use flat=True to return a QuerySet of single values instead of 1-tuples:

<QuerySet [1, 2]>

回答2:

values()

Returns a QuerySet that returns dictionaries, rather than model instances, when used as an iterable.

values_list()

Returns a QuerySet that returns list of tuples, rather than model instances, when used as an iterable.

distinct()

distinct are used to eliminate the duplicate elements.

Example:

Article.objects.values_list('id', flat=True) # flat=True will remove the tuples and return the list   
[1, 2, 3, 4, 5, 6]

Article.objects.values('id')
[{'id':1}, {'id':2}, {'id':3}, {'id':4}, {'id':5}, {'id':6}]

回答3:

You can get the different values with:

set(Article.objects.values_list('comment_id', flat=True))