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JMG
JMG

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Custom Commands in Django

#django #beginners #python #tutorial

Hello there! We are going to learn how to write simple custom Django commands. I will break down this lesson into 3 sections;

  • Introduction
  • Setting up the commands
  • Calling the commands

Introduction

  • Create a generic Django project called resource_center.
  • Make migrations and migrate your database.
  • Create a Django app called books. Register this app in settings.py
  • In your book/models.py create a model Book as shown below; 
# books/models.py  from django import models class Book(models.Model): name = models.CharField(max_length=50) author = models.CharField(max_length=20)
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  • Make migrations and migrate your database.

Setting Up Commands

Django convention dictates that custom commands have to live inside the project/app/management/commands directory of your project. In this case, this will be resource_center/management/commands.
Navigate to your books folder and create a folder named management. Create a subfolder called commands.
Create a file inside the commands folder and name it books_creator.py.
Add the following code;

# resource_center/books/management/commands/books_creator.py from django.core.management.base import BaseCommand from resource_center.books.models import Book class Command(BaseCommand): help = "Create initial data for the project" def add_arguments(self, parser): # Positional arguments  parser.add_argument("count", help="Any number", type=int) # Named (optional) arguments  parser.add_argument( "--delete", help="Delete books instead of creating them", ) def handle(self, *args, **kwargs): count = kwargs.get("count") print(f"The current count is {count}") if kwargs["delete"]: Book.objects.all().delete() else: Book.objects.get_or_create( name="The Lord of the Rings", author="J.R.R. Tolkien" ) Book.objects.get_or_create( name="The Hobbit", author="J.R.R. Tolkien" )
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Our class Command inherits from Django's BaseCommand.
The class variable help describes what the custom command aims to achieve, more like the help_text in your model fields.

The method add_arguments is used to instruct the command to expect arguments which may be optional.

The method handle handles (pun intended 😅) your logic.

Calling the commands

To call your commands, call them in the following format;
python manage.py <custom_command_file_name>. Do not include the file's .py extension.
In this case, our command will be called as

python manage.py books_creator <count>

The count is any number of your choice. This is a positional argument that we can not ignore. If ignored, it will raise the following error; manage.py books_creator: error: the following arguments are required: count.

The command with our count positional argument will be as follows;
python manage.py books_creator 16

If you add the optional named arguments, you get a command like this;
python manage.py books_creator 16 --delete=true

That's it!

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