Copying model instances

Although there is no built-in method for copying model instances, it is possible to easily create new instance with all fields' values copied. In the simplest case, you can just set pk to None. Using our blog example:

blog = Blog(name='My blog', tagline='Blogging is easy') 
blog.save() # blog.pk == 1 
 
blog.pk = None 
blog.save() # blog.pk == 2 

Things get more complicated if you use inheritance. Consider a subclass of Blog:

class ThemeBlog(Blog): 
    theme = models.CharField(max_length=200) 
 
django_blog = ThemeBlog(name='Django', tagline='Django is easy',
  theme='python') 
django_blog.save() # django_blog.pk == 3 

Due to how inheritance works, you have to set both pk and id to None:

django_blog.pk = None 
django_blog.id = None 
django_blog.save() # django_blog.pk == 4 

This process does not copy related objects. If you want to copy relations, you have to write a little bit more code. In our example, Entry has a many to many field to Author:

entry = Entry.objects.all()[0] # some previous entry 
old_authors = entry.authors.all() 
entry.pk = None 
entry.save() 
entry.authors = old_authors # saves new many2many relations