CODEWITHSUNDEEP
pythondjangoorm
jacquel
jacquel

Reputation: 1026

difference between objects.create() and object.save() in django orm

u = UserDetails.objects.create(first_name='jake',last_name='sullivan')
u.save()

UserDetails.objects.create() and u.save() both perform the same save() function. What is the difference? Is there any extra check or benefit in using create() vs save()?

Similar questions:

Upvotes: 81

Views: 77394

Answers (3)

Emmanuel Whesu
Emmanuel Whesu

Reputation: 1

My thought on this is that you should user=User.objects.create(name=name, location=location) for instance when creating a new User object and use an instance of user.save() when you are modifying the user object.

Upvotes: 0

Furkan Siddiqui
Furkan Siddiqui

Reputation: 2025

Similar question: Django Model() vs Model.objects.create()

The difference between Model() vs Model.objects.create() are summarized as below.

  1. .save() perform internally as either INSERT or UPDATE object to db, while .objects.create() perform only INSERT object to db.

    Model.save() perform ....

    UPDATE → If the object’s primary key attribute is set to a value that evaluates to True

    INSERT → If the object’s primary key attribute is not set or if the UPDATE didn’t update anything (e.g. if primary key is set to a value that doesn’t exist in the database).

  1. If primary key attribute is set to a value then Model.save() perform UPDATE but Model.objects.create raise IntegrityError.

    eg.

    models.py

    class Subject(models.Model):
   subject_id = models.PositiveIntegerField(primary_key=True, db_column='subject_id')
   name = models.CharField(max_length=255)
   max_marks = models.PositiveIntegerField()

    1) Insert/Update to db with Model.save()

    physics = Subject(subject_id=1, name='Physics', max_marks=100)
physics.save()
math = Subject(subject_id=1, name='Math', max_marks=50)  # Case of update
math.save()

    Output:

    Subject.objects.all().values()
<QuerySet [{'subject_id': 1, 'name': 'Math', 'max_marks': 50}]>

    2) Insert to db with Model.objects.create()

    Subject.objects.create(subject_id=1, name='Chemistry', max_marks=100)
IntegrityError: UNIQUE constraint failed: m****t.subject_id

    Explanation: Above math.save() is case of update since subject_id is primary key and subject_id=1 exists django internally perform UPDATE, name Physics to Math and max_marks from 100 to 50 for this, but objects.create() raise IntegrityError

  1. Model.objects.create() not equivalent to Model.save() however same can be achieved with force_insert=True parameter on save method i.e Model.save(force_insert=True).
  1. Model.save() return None where Model.objects.create() return model instance i.e. package_name.models.Model

Conclusion: Model.objects.create() internally do model initialization and perform save with force_insert=True.

source-code block of Model.objects.create()

def create(self, **kwargs):
    """
    Create a new object with the given kwargs, saving it to the database
    and returning the created object.
    """
    obj = self.model(**kwargs)
    self._for_write = True
    obj.save(force_insert=True, using=self.db)
    return obj

The following links can be followed for more details:

  1. https://docs.djangoproject.com/en/stable/ref/models/querysets/#create

  2. https://github.com/django/django/blob/2d8dcba03aae200aaa103ec1e69f0a0038ec2f85/django/db/models/query.py#L440

Note: Above answer is from question.

Upvotes: 19

Maxime Lorant
Maxime Lorant

Reputation: 36161

The Django documentation says it is the same. It is just more convenient to make it on one line. You could make a save() on one line too, but it would be more verbose and less readable -- it is clear you are creating a new object with the create() method.

create(**kwargs)

A convenience method for creating an object and saving it all in one step. Thus:

p = Person.objects.create(first_name="Bruce", last_name="Springsteen")

and:

p = Person(first_name="Bruce", last_name="Springsteen")
p.save(force_insert=True)

are equivalent.

The force_insert parameter is documented elsewhere, but all it means is that a new object will always be created. Normally you won’t need to worry about this. However, if your model contains a manual primary key value that you set and if that value already exists in the database, a call to create() will fail with an IntegrityError since primary keys must be unique. Be prepared to handle the exception if you are using manual primary keys.

Upvotes: 110

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