问题
Based on the Django doc, I should be able to pass multiple objects at once to be added to a manytomany relationship but I get a
* TypeError: unhashable type: 'list'
when I try to pass a django queryset casted in a list. Passing a Queryset or a ValuesListQueryset seems to fail also. Is there a better way than use a for loop ?
回答1:
Use: object.m2mfield.add(*items) as described in the documentation:
add() accepts an arbitrary number of arguments, not a list of them.
add(obj1, obj2, obj3, ...)
To expand that list into arguments, use *
add(*[obj1, obj2, obj3])
Addendum:
Django does not call obj.save() for each item but uses bulk_create(), instead.
回答2:
To add on, If you want to add them from a queryset
Example
# Returns a queryset
permissions = Permission.objects.all()
# Turns it into a list
permissions = list(permissions)
# Add the results to the many to many field (notice the *)
group = MyGroup.objects.get(name='test')
group.permissions.add(*permissions)
From: Insert queryset results into ManytoManyfield
回答3:
Django 1.9 adds additional ways for adding to a many-to-many relationship.
Documentation: https://docs.djangoproject.com/en/1.9/ref/models/relations/#django.db.models.fields.related.RelatedManager.set
set is a new nicety:
>>> new_list = [obj1, obj2, obj3]
>>> e.related_set.set(new_list)
来源：https://stackoverflow.com/questions/4959499/how-to-add-multiple-objects-to-manytomany-relationship-at-once-in-django