How to convert a list in to queryset django

Question

I have a queryset(which is filtered actually) as below

posts = [<Post: published>, <Post: needs>, <Post: be>, <Post: issues>, <Post: to>, <Post: tags>]

But i need to filter the above queryset manually with the some field coming from another table/place etc.

so i had filtered something like below

custom_list = []

for rec in posts:
    if 'string_or_field' in rec.tags.all():
        custom_list.extend(rec)

        or

custom_list = [rec for rec in posts if 'string_or_field' in rec.tags.all()]

So as we can observe above we are creating a list by filtering a queryset, but i want the result as a queryset.

So is there any way to convert the list to queryset object ?

Why exactly do you need an actual queryset? The point of duck-typing is that you should be able to use any list-like construct. — Daniel Roseman
– Daniel Roseman, Commented Sep 4, 2013 at 8:38
yes actually i need a queryset to perform some operations since it is an object, but i got a list as above , so want to convert the resultant list to queryset — Shiva Krishna Bavandla
– Shiva Krishna Bavandla, Commented Sep 4, 2013 at 13:03

Shiva Krishna Bavandla · Accepted Answer · 2013-09-04 07:43:07Z

19

Actually i had found one way by googling, but this may take a lot of time for querying/generating results if there are huge number of records

custom_list = [rec.id for rec in posts if 'string_or_field' in rec.tags.all()]

querset = MyModel.objects.filter(id__in=custom_list)

answered Sep 4, 2013 at 7:43

Shiva Krishna Bavandla

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1 Comment

oruchkin Over a year ago

this is exactly what he asked, this shoud be accepted answer

Paulo Almeida · Accepted Answer · 2013-09-04 09:43:51Z

18

You can query the Tag object first and filter Post with those ids:

tags = Tag.objects.filter(field_name='string_or_field')
posts = Post.objects.filter(tags__in=tags)

answered Sep 4, 2013 at 9:43

Paulo Almeida

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1 Comment

Leopd Over a year ago

If you need the queryset to be sorted in the same order as the list, see stackoverflow.com/a/61686789/303056

Ilya Petukhov · Accepted Answer · 2019-10-31 09:46:45Z

6

The previous answers are correct if each list item already exists in the database, but sometimes this is not the case. In this case you can create a queryset stub based on the list and implement queryset-methods and queryset-properties as needed.

class ListAsQuerySet(list):

    def __init__(self, *args, model, **kwargs):
        self.model = model
        super().__init__(*args, **kwargs)

    def filter(self, *args, **kwargs):
        return self  # filter ignoring, but you can impl custom filter

    def order_by(self, *args, **kwargs):
        return self

qs = ListAsQuerySet(custom_list, model=Post)

answered Oct 31, 2019 at 9:46

Ilya Petukhov

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3 Comments

alias51 Over a year ago

This doesn't work. For a start you can't pass model to a class.

Ilya Petukhov Over a year ago

Why? This works for me. Give me more information to resolve your problem.

Samuel Kazeem Over a year ago

To pass this to a formset add an ordered method to the class.

alias51 · Accepted Answer · 2020-02-10 14:34:12Z

4

Here's a simple util that you can run to produce a QS from a list:

def list_to_queryset(model, data):
    from django.db.models.base import ModelBase

    if not isinstance(model, ModelBase):
        raise ValueError(
            "%s must be Model" % model
        )
    if not isinstance(data, list):
        raise ValueError(
            "%s must be List Object" % data
        )

    pk_list = [obj.pk for obj in data]
    return model.objects.filter(pk__in=pk_list)

answered Feb 10, 2020 at 14:34

alias51

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Comments

Alexandr Sergeevich · Accepted Answer · 2024-02-15 19:33:41Z

0

from typing import Type

from django.db.models import Model


def list_to_queryset(model: Type[Model], data: list):

    assert issubclass(model, Model), "%s must be Model" % model
    assert isinstance(data, list), "%s must be List Object" % data

    pk_list = [obj.pk for obj in data]
    return model.objects.filter(pk__in=pk_list)

answered Feb 15, 2024 at 19:33

Alexandr Sergeevich

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2 Comments

Community Over a year ago

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.

Jeremy Caney Over a year ago

Thank you for contributing to the Stack Overflow community. This may be a correct answer, but it’d be really useful to provide additional explanation of your code so developers can understand your reasoning. This is especially useful for new developers who aren’t as familiar with the syntax or struggling to understand the concepts. Would you kindly edit your answer to include additional details for the benefit of the community?

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