Producing a list by summing results of 'values_list' in Django queryset

Question

Through a Django queryset call, I'm generating a list of integer tuples:

[(0,1),(0,2),(0,4),(5,8),.......]

I instead need to generate a list which sums the two elements inside the tuple together, ie

[1,2,4,13,.....]

How can I accomplish that within the Django queryset query?

The query I've written so far is:

photos_score_list = Photo.objects.filter(upload_time__gte=yesterday).annotate(unique_comments=Count('photocomment__submitted_by', distinct=True)).values_list('vote_score','unique_comments')

Answer 1

I don't know about Django, but when you have this:

l = [(0,1),(0,2),(0,4),(5,8)]

you can compute the sum of each element in one line using list comprehension:

l2 = [sum(x) for x in l]

result:

[1, 2, 4, 13]

applied to your problem:

photos_score_sum = [sum(x) for x in Photo.objects.filter(upload_time__gte=yesterday).annotate(unique_comments=Count('photocomment__submitted_by', distinct=True)).values_list('vote_score','unique_comments')]

Answer 2

Once you have that list of tuples, you can use a list comprehension to generate your second list like below:

>>> tuples_list = [(0,1),(0,2),(0,4),(5,8)]
>>> res_list = [i+j for i,j in tuples_list]
>>> res_list
[1, 2, 4, 13]

In our list comprehension, we return for tuple (i,j) in tuples_list the sum i+j and the result is sorted in res_list .