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blank=True – Django Built-in Field Validation
  • Last Updated : 13 Feb, 2020
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Built-in Field Validations in Django models are the default validations that come predefined to all Django fields. Every field comes in with built-in validations from Django validators. One can also add more built-in field validations for applying or removing certain constraints on a particular field. blank=True will make the field accept blank values. It simply means that field can be empty.

Syntax

field_name = models.Field(blank = True)

Django Built-in Field Validation blank=True Explanation

Illustration of null=True 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. We will be using CharField for experimenting for all field options.






from django.db import models
from django.db.models import Model
# Create your models here.
  
class GeeksModel(Model):
    geeks_field = models.CharField(max_length = 200, blank = True)

After running makemigrations and migrate on Django and rendering the above model, let us try to create an instance using None from Django shell. To start Django shell, enter the command,

Python manage.py shell

Now let us try to create instance of GeeksModel using empty string.




# importing required model
from geeks.models import GeeksModel
  
# creating instance of GeeksModel
s = GeeksModel.objects.create(geeks_field = "")
  
# saving current model instance
s.save()

Let us check in admin interface if the instance of model is created.
null=True - Django Built-in Field Validation
Therefore, blank=True modifies the field to accept empty values or in python’s terms “” Values.

Advanced Concepts with blank=True

Note that this is different than null. null is purely database-related, whereas blank is validation-related. If a field has blank=True, form validation will allow entry of an empty value. If a field has blank=False, the field will be required. null=True and blank=True are often used simulatneously. The combo of the two is so frequent because typically if you’re going to allow a field to be blank in your form, you’re going to also need your database to allow NULL values for that field.

More Built-in Field Validations

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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