How to mix queryset results?

Question

I have query:

items = MyModel.objects.all().order_by('nr')[:10]

and I get 10 items with higher number. Now I have to mix these results. How to do it?

What do you mean by "mix"? Do you want to shuffle them randomly? — moopet, Aug 22 '12 at 12:44

AndyTheEntity · Answer 1 · 2018-01-05T18:17:55.360

33

Curiously, this not very well documented feature works:

Country.objects.order_by('?')

Astonishingly, the existing documentation has very little Google juice, unless you search for "randomly" rather than "random".

edited Jan 05 '18 at 18:17

answered Aug 25 '14 at 15:11

AndyTheEntity

6

The reason why it's not very well documented is because doing it that way is going to cause huge performance issues on larger databases. http://stackoverflow.com/questions/1731346/how-to-get-two-random-records-with-django#6405601 – Llanilek May 24 '15 at 11:06
https://docs.djangoproject.com/en/3.0/ref/models/options/#ordering – suhailvs Jun 02 '20 at 08:25

score 21 · Accepted Answer · answered Aug 22 '12 at 13:08

21

You can't reorder a query once a slice has been taken, so use different approach

import random
items = sorted(MyModel.objects.all().order_by('nr')[:10], key=lambda x: random.random())

answered Aug 22 '12 at 13:08

Sergey Lyapustin

score 17 · Answer 3 · answered Aug 22 '12 at 13:10

17

OK, you can't re-order a queryset after you've pulled it in, but you can do this instead

import random
items = list(MyModel.objects.all().order_by('nr')[:10])
random.shuffle(items)

answered Aug 22 '12 at 13:10

moopet

Would the downvoter like to comment as to why this isn't an appropriate answer, and I'll update it? – moopet Sep 01 '16 at 15:36
3

This is a perfectly appropriate answer. Here is my upvote. – Forethinker Aug 22 '18 at 03:21

3 Answers3