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UUIDField – Django Models

  • Difficulty Level : Basic
  • Last Updated : 12 Feb, 2020
Geek Week

UUIDField is a special field to store universally unique identifiers. It uses Python’s UUID class. UUID, Universal Unique Identifier, is a python library that helps in generating random objects of 128 bits as ids. It provides the uniqueness as it generates ids on the basis of time, Computer hardware (MAC etc.). Universally unique identifiers are a good alternative to AutoField for primary_key. The database will not generate the UUID for you, so it is recommended to use default.

For example,




import uuid
from django.db import models
  
class MyUUIDModel(models.Model):
    id = models.UUIDField(
         primary_key = True,
         default = uuid.uuid4,
         editable = False)
    # other fields

Syntax

field_name = models.UUIDField(**options)

Django Model UUIDField Explanation

Illustration of UUIDField using an Example. Consider a project named geeksforgeeks having an app named geeks.

Refer to the following articles to check how to create a project and an app in Django.



Enter the following code into models.py file of geeks app.




from django.db import models
from django.db.models import Model
# Create your models here.
  
class GeeksModel(Model):
    geeks_field = models.UUIDField()

Add the geeks app to INSTALLED_APPS




# Application definition
  
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'geeks',
]

Now when we run makemigrations command from the terminal,

Python manage.py makemigrations

A new folder named migrations would be created in geeks directory with a file named 0001_initial.py




# Generated by Django 2.2.5 on 2019-09-25 06:00
  
from django.db import migrations, models
  
class Migration(migrations.Migration):
  
    initial = True
  
    dependencies = [
    ]
  
    operations = [
        migrations.CreateModel(
            name ='GeeksModel',
            fields =[
                ('id'
                  models.AutoField(auto_created = True,
                  primary_key = True,
                  serialize = False
                  verbose_name ='ID'
                )),
                ('geeks_field'
                  models.UUIDField()
                 )),
            ],
        ),
    ]

Thus, an geeks_field UUIDField is created when you run makemigrations on the project.It is a field to store python’s UUID instance.

How to use UUIDField ?

UUID, Universal Unique Identifier, is a python library which helps in generating random objects of 128 bits as ids. To know more about UUID visit Generating Random id’s using UUID in Python. Let’s try to save a uuid object into the UUIDField.




# importing the model
# from geeks app
from geeks.models import GeeksModel
  
# importing uuid
import uuid
  
# creating an instance of
# uuid object
test = uuid.uuid4()
  
# creating a instance of 
# GeeksModel
geek_object = GeeksModel.objects.create(geeks_field = test)
geek_object.save()

Now let’s check it in admin server. We have created an instance of GeeksModel
UUIDField-django-models

Field Options

Field Options are the arguments given to each field for applying some constraint or imparting a particular characteristic to a particular Field. For example, adding an argument null = True to UUIDField will enable it to store empty values for that table in relational database.
Here are the option and attributes that an UUIDField can use.

Field OptionsDescription
NullIf True, Django will store empty values as NULL in the database. Default is False.
BlankIf True, the field is allowed to be blank. Default is False.
db_columnThe name of the database column to use for this field. If this isn’t given, Django will use the field’s name.
DefaultThe default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created.
help_textExtra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form.
primary_keyIf True, this field is the primary key for the model.
editableIf False, the field will not be displayed in the admin or any other ModelForm. They are also skipped during model validation. Default is True.
error_messagesThe error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override.
help_textExtra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form.
verbose_nameA human-readable name for the field. If the verbose name isn’t given, Django will automatically create it using the field’s attribute name, converting underscores to spaces.
validatorsA list of validators to run for this field. See the validators documentation for more information.
UniqueIf True, this field must be unique throughout the table.

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