How to select a record and update it, with a single queryset in Django?

Use the queryset object update method:

MyModel.objects.filter(pk=some_value).update(field1='some value')

Django database objects use the same save() method for creating and changing objects.

obj = Product.objects.get(pk=pk)obj.name = "some_new_value"obj.save()

How Django knows to UPDATE vs. INSERT
If the object’s primary key attribute is set to a value that evaluates to True (i.e., a value other than None or the empty string), Django executes an UPDATE. If the object’s primary key attribute is not set or if the UPDATE didn’t update anything, Django executes an INSERT.

Ref.: https://docs.djangoproject.com/en/1.9/ref/models/instances/

This answer compares the above two approaches.If you want to update many objects in a single line, go for:

# Approach 1MyModel.objects.filter(field1='Computer').update(field2='cool')

Otherwise you would have to iterate over the query set and update individual objects:

#Approach 2    objects = MyModel.objects.filter(field1='Computer')for obj in objects:    obj.field2 = 'cool'    obj.save()

1. Approach 1 is faster because, it makes only one database query, compared to approach 2 which makes 'n+1' database queries. (For n items in the query set)

2. Fist approach makes one db query ie UPDATE, the second one makes two: SELECT and then UPDATE.

3. The tradeoff is that, suppose you have any triggers, like updating updated_on or any such related fields, it will not be triggered on direct update ie approach 1.

4. Approach 1 is used on a queryset, so it is possible to update multiple objects at once, not in the case of approach 2.