如何将 django 查询集中所有对象的字段更改为一个值但我不想保存它

Question

I have two models Question and Choice .

Here I want to change the value of all choice.vote to 0 . But I don't want to update it.

I know I can update the field by calling query_set.update(field=value) .

Extra requirements:

• I don't want to affect anything to my database
• also, more importantly, I want to avoid this nested for loop .

Any help will be appreciated.

updated_choice_list = []
for question in Question.objects.filter(some_condition):
    for choice in question.choice_set.all():
        choice.vote = 0 # I dont want to save the choice vote
        updated_choice_list.append(choice)

Answer 1

According to the details you've given this should do it.

choices = [c for c in Choice.objects.filter(question__some_filter=something).all()]
for c in choices:
    c.vote = 0

Answer 2

Your current code doesn't change anything in the database, so that is done. Depending on your some_condition you can remove the nested for loops, by querying the Choices directly:

updated_choice_list = Choice.objects.filter(question__some_condition):
for choice in updated_choice_list:
    choice.vote = 0