BinaryField – Django Models

BinaryField is a special field to store raw binary data. It can be assigned bytes, bytearray, or memoryview. By default, BinaryField sets editable to False, that is it can’t be included in a ModelForm. Since BinaryField stores raw data or in other terms a python object, it can not be manually entered and needs to be assigned through a view or django shell. This is what editable to False means, that is it can’t be edited through any form.

Syntax

field_name = models.BinaryField(**options)

Django Model BinaryField Explanation

Illustration of BinaryField 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.

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

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Add the geeks app to INSTALLED_APPS

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

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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

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# 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.BinaryField()),
            ],
        ),
    ]

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Thus, an geeks_field BigIntegerField is created when you run makemigrations on the project.It is a field to store raw binary data.

How to use BinaryField ?

Any type of data can be converted into bytes including integers, srings, images, etc. Let’s try to save a string into the BinaryField. String can be converted to bytes using the generic bytes function. This function internally points to CPython Library which implicitly calls the encode function for converting the string to specified encoding.

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# importing the model
# from geeks app
from geeks.models import GeeksModel
  
# creating a string
test_string = "GFG is best"
  
# creating a bytes object
res = bytes(test_string, 'utf-8')
  
# creating a instance of 
# GeeksModel
geek_object = GeeksModel.objects.create(geeks_field = res)
geek_object.save()

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

As specified, BinaryField is a non-editable field, if you manually try to make it editable using editable=True it will create unexpected errors. It should be created in a function so that objects can be allocated to it.

binaryfield-editable-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 BinaryField will enable it to store empty values for that table in relational database.
Here are the option and attributes that an BinaryField can use.

Field Options Description
Null If True, Django will store empty values as NULL in the database. Default is False.
Blank If True, the field is allowed to be blank. Default is False.
Choices An iterable (e.g., a list or tuple) of 2-tuples to use as choices for this field.
Default The 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_text Extra “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_key If True, this field is the primary key for the model.
Unique If True, this field must be unique throughout the table.


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