Django model object with foreign key creation

Question

Hi Suppose I have a simple model class like this:

class TestModel(models.Model):
    testkey = models.ForeignKey(TestModel2)
    ...

When I am creating a TestModel object I have to pass to it an instance of the TestModel2 object to create it:

testkey =TestModel2.objects.get(id=...)
TestModel.objects.create(testkey=testkey)

This results in 2 queries to database I suppose, and I have a list of Foreign key IDs that I need to create objects with.

Is it possible to create objects with foreign keys without initially retrieving the foreign key objects?

Possible duplicate of [Django: Set foreign key using integer?](http://stackoverflow.com/questions/2846029/django-set-foreign-key-using-integer) — Ciro Santilli OurBigBook.com, May 25 '16 at 15:05

score 137 · Accepted Answer · edited Sep 08 '21 at 14:08

137

What you’re after is:

TestModel.objects.create(testkey_id=1)

edited Sep 08 '21 at 14:08

Daniel Benedykt

answered Nov 16 '10 at 14:56

sneeu

1

Yes, you're right, but for some reason it does not work with get_or_create :( – dragoon Nov 16 '10 at 15:01
2

@dragon: I believe TestModel2.objects.get(testkey_id=1) doesn't work either. – Tomasz Zieliński Nov 16 '10 at 20:30
16

@Tomasz no, that won’t work, but `TestModel2.objects.get(testkey__id=1)`, and `TestModel2.objects.get_or_create(testkey__id=1)` will work (note the double underscore). It’s very possible though that these will raise `MultipleObjectsReturned`. – sneeu Nov 16 '10 at 22:19
1

What if the foreign key has a to_field value that is different than "id"? – kloddant Oct 12 '20 at 16:52
2

@kloddant as far as I can tell, the field is always called `«foreign-key-name»_id` regardless of `to_field` or the primary-key of the related model. – sneeu Oct 15 '20 at 10:56
@sneeu, Thanks! Yes, I have confirmed this just yesterday by testing it out. It is indeed «foreign-key-name»_id, regardless of the to_field. – kloddant Oct 15 '20 at 13:32

score 18 · Answer 2 · answered Dec 11 '20 at 19:01

18

In my case TestModel.objects.create(testkey__id=1) didn't work for me so I had to put one underscore instead of two, for example

TestModel.objects.create(testkey_id=1)

answered Dec 11 '20 at 19:01

Zohab Ali

1

confirm, single underscore seems to work (Django 3.1.7) – tikej Mar 16 '21 at 13:26
1

According to another [answer](https://stackoverflow.com/a/2846537/2089675), this is the correct method – smac89 Jul 14 '21 at 17:27

score 12 · Answer 3 · edited Jan 04 '19 at 12:25

12

In get_or_create it will fail in get. So to make get_or_create work below is the solution:

TestModel.objects.get_or_create(testkey=TestModel2(id=1))

edited Jan 04 '19 at 12:25

4b0

answered Jan 04 '19 at 11:31

Dhruvil Amin

3 Answers3