Django queryset filter max values for list

Question

I'm wondering if there is any way to pass a list to a django queryset and limit to the max/min/latest/oldest value for each item in the list.

Basically something like this:

serial_list = [2231, 2232, 2233]
data_queryset = Data.objects.filter(serial__in=serial_list).latest()

I'm fully aware that the above code doesn't work. I'm just trying to illustrate a queryset that would return the .latest() value for each object where the serial is in serial_list.

That code does work, have you tried with a date field e.g.: Data.objects.filter(serial__in=serial_list).latest('date_field_name') ? — heemayl
– heemayl, Commented Jan 15, 2018 at 23:02
@heemayl that only returns a single object; The latest object in the queryset. I'm trying to get a latest object for each item in the list. So in this case, the queryset should have three objects. The latest for each serial in the list. — Jon
– Jon, Commented Jan 15, 2018 at 23:27

heemayl · Accepted Answer · 2018-01-15 23:38:36Z

1

You can iterate over the serial_list, and for each one get the latest() element from the queryset after querying the model. Here, using a dict comprehension to set each iterated item from serial_list as key and relevant latest() item on queryset as value:

serial_list = [2231, 2232, 2233]
{serial_: Data.objects.filter(serial=serial_).latest('date_field') \
           for serial_ in serial_list}

answered Jan 15, 2018 at 23:38

heemayl

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1 Comment

Jon Over a year ago

This works! I hadn't thought to use a dictionary like that

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