django-models Getting started with django-models

Remarks

Django Model example

A simple example would be for a library management application; you would have 2 models, for example, student and book

in models.py:

from django.db import models

class student(models.Model):
    roll_no = models.IntegerField(primary_key=True)
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)
 

Here we have given roll_no a primary key to the student model, but even if we don't give a primary key to any attribute, Django would automatically assign an attribute called id , which would be automatically assigned and incremented on the creation of new rows.

Now you can just import this model into your views or in a project and interact with it by simply creating an object of that model.

Django has many inbuilt Fields available, or even you can create your own as well.

Django also supports relationships between models, many-to-many , one-to-one , many-to-one .

Django's detailed doc for Models

Installation or Setup

Generally, each model maps to a single database table.We to write the field type,limits,size,etc in model.py file of the app. This will create the necessary table and fields in the database.

'''   models.py    '''
from django.db import models
    
    class table_name(models.Model):
        field_name= models.field_type(conditions)
 

Next we need to inform Django in settinggs.py about the app which will be using this model.

    '''  settinggs.py  ''''
    
    INSTALLED_APPS = [
    #...
    'app_name',
    #...    ]
 

We are almost done. Next we need to migrate this app so that database tables are created. In terminal type the following:

python manage.py migrate
 

migrate will create the necessary databases by checking the app_installed in the setting.py

By makemigrations , Django will know the changes that are made to the models.

python manage.py makemigrations
 

That's it. Your database is created and you can see the schema in the terminal

python manage.py sqlmigrate app_name 0001
 

What is Django models?

A Django model typically refers to a table in the database, attributes of that model becomes the column of that table. In more of a real-world example, you would create a model for any entity in your application, and store its attributes with django fields which automatically handles data-types conversions for the database you would be using.

One of the great features for Django is its ORM , you don't have to write any database query, and even it's recommended NOT to write one when using Django. ORM converts your Django models and all the operations you do with it to the corresponding database queries. This means that all the manipulation you have to do, it now with the python objects created out from that model, and all the underlying database stuff would be taken care by Django's ORM . There are a bunch of tweaks and customizations you could do with it.

Django's ORM supports all the major database like Postgres , MySQL , sqlite3 , and other enterprises database provided with proper drivers. This also means that you don't have to care what underlying database you are using, or even if you want to shift from one database from another, you can do it without changing a single line of your application logic, just change the database string from settings.py , dump the old data, and you should be good to go.