class OneToOneField(othermodel, on_delete, parent_link=False, **options) [source]
A one-to-one relationship. Conceptually, this is similar to a ForeignKey with unique=True, but the “reverse” side of the relation will directly return a single object.
on_delete can now be used as the second positional argument (previously it was typically only passed as a keyword argument). It will be a required argument in Django 2.0.
This is most useful as the primary key of a model which “extends” another model in some way; Multi-table inheritance is implemented by adding an implicit one-to-one relation from the child model to the parent model, for example.
One positional argument is required: the class to which the model will be related. This works exactly the same as it does for ForeignKey, including all the options regarding recursive and lazy relationships.
If you do not specify the related_name argument for the OneToOneField, Django will use the lower-case name of the current model as default value.
With the following example:
1 2 3 4 5 6 7 8 9 10 11 12 13 | from django.conf import settingsfrom django.db import modelsclass MySpecialUser(models.Model): user = models.OneToOneField( settings.AUTH_USER_MODEL, on_delete=models.CASCADE, ) supervisor = models.OneToOneField( settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name='supervisor_of', ) |
your resulting User model will have the following attributes:
1 2 3 4 5 | >>> user = User.objects.get(pk=1)>>> hasattr(user, 'myspecialuser')True>>> hasattr(user, 'supervisor_of')True |
A DoesNotExist exception is raised when accessing the reverse relationship if an entry in the related table doesn’t exist. For example, if a user doesn’t have a supervisor designated by MySpecialUser:
1 2 3 4 | >>> user.supervisor_ofTraceback (most recent call last): ...DoesNotExist: User matching query does not exist. |
Additionally, OneToOneField accepts all of the extra arguments accepted by ForeignKey, plus one extra argument:
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