如何计算Django中两个日期之间的平均差? [英] How do I calculate the average difference between two dates in Django?

问题描述

使用Django和Python 3.7.我正在尝试编写查询以给我两个日期之间的差异的平均值.我的模型中有两个字段，均为"DateTimeField"，我尝试像这样计算平均差

Using Django and Python 3.7. I'm tryhing to write a query to give me the average of the difference between two dates. I have two fields in my model, both "DateTimeField"s, and I try to calculate the average difference like so

everything_avg = Article.objects.aggregate(
    avg_score=Avg(F('removed_date') - F('created_on'), output_field=models.DateTimeField())
).filter(removed_date__isnull=False)
return everything_avg

但是运行以上命令时我最终收到此错误

but I end up getting this error when running the above

AttributeError: 'dict' object has no attribute 'filter'

什么是获得我的平均值的正确方法?

What's the right way to get my average?

推荐答案

如文档所述:

aggregate()是QuerySet的终端子句，该子句在调用时返回名称-值对的字典. *

aggregate方法返回一个字典，因此您需要先对其进行过滤.因此，如果您按照以下方式更改代码，则会得到结果:

aggregate method returns a dictionary, thus you need to make your filtering before it. Thus if you alter your code as following you would get your result:

everything_avg = Article.objects.filter(removed_date__isnull=False)\
    .aggregate(
        avg_score=Avg(
            F('removed_date') - F('created_on'),
            output_field=models.DateTimeField()
        )
    )
return everything_avg

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