DecimalField - Django Models

DecimalField is a field which stores a fixed-precision decimal number, represented in Python by a Decimal instance. It validates the input using DecimalValidator

Syntax

field_name = models.DecimalField(max_digits=None, decimal_places=None, **options)

Parameters:

• max_digits: The maximum number of digits allowed in the number, including digits before and after the decimal point.
• decimal_places: The number of decimal places to store.

Note: max_digits must be greater than or equal to decimal_places.

Example Usage:

To store numbers up to 999 with a resolution of 2 decimal places:

models.DecimalField(..., max_digits=5, decimal_places=2)

And to store numbers up to approximately one billion with a resolution of 10 decimal places:

models.DecimalField(..., max_digits=19, decimal_places=10)

Django Model DecimalField

Illustration of DecimalField 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.

• How to Create a Basic Project using MVT in Django?
• How to Create 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.DecimalField(
        max_digits = 5,
        decimal_places = 2
    )

Adding the App to INSTALLED_APPS:

Make sure to add the geeks app to your project's INSTALLED_APPS in settings.py:

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'geeks',    # Add this line 
]

Migrations

To create the database schema for your model, run the following commands:

1. Create migrations:

python manage.py makemigrations

2. Apply migrations:

python manage.py migrate

This will create the GeeksModel and add a geeks_field DecimalField to the database.

How to use DecimalField

DecimalField is used for storing decimal numbers (e.g., monetary values, precise measurements) in the database.

Here’s how you can store a decimal number in the GeeksModel:

# importing the model from geeks app
from geeks.models import GeeksModel

# importing the decimal module
import decimal

# creating a Decimal instance
d = decimal.Decimal(9.53)

# creating an instance of GeeksModel and saving it
geek_object = GeeksModel.objects.create(geeks_field=d)
geek_object.save()

Now, this decimal value 9.53 will be stored in the database in the geeks_field column and we can check it in admin server.

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 DecimalField will enable it to store empty values for that table in relational database. Here are the field options and attributes that a DecimalField can use.