Django: how to create custom "base" model

You need to create an abstract base class having these common fields and then inherit this base class in your models.

Step-1: Create a new Abstract Base Class

We first create an abstract base class called BaseModel. This BaseModel class contains the 3 model fields creation_date, valididity_start_date and validity_end_date which are common in almost every model of yours.

In the inner Meta class, we set abstract=True. This model will then not be used to create any database table. Instead, when it is used as a base class for other models, its fields will be added to those of the child class.

class BaseModel(models.Model):  # base class should subclass 'django.db.models.Model'

    creation_date = models.DateTimeField(..) # define the common field1
    validity_start_date = models.DateTimeField(..) # define the common field2
    validity_end_date = models.DateTimeField(..) # define the common field3

    class Meta:
        abstract=True # Set this model as Abstract

Step-2: Inherit this Base class in your models

After creating the abstract base class BaseModel, we need to inherit this class in our models. This can be done using normal inheritance as done in Python.

class MyModel1(BaseModel): # inherit the base model class

    # define other non-common fields here
    ...

class MyModel2(BaseModel): # inherit the base model class

    # define other non-common fields here
    ...

Here, MyModel1 and MyModel2 classes contain the 3 fields creation_date, valididity_start_date and validity_end_date from the base class BaseModel apart from the other model fields defined in it.

class Basetable(models.Model):

   created_on = models.DateTimeField(auto_now_add=True)
   modified_on = models.DateTimeField(auto_now=True)
   created_by = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='%(class)s_createdby')
   modified_by = models.ForeignKey(settings.AUTH_USER_MODEL,
                                related_name='%(class)s_modifiedby', null=True, blank=True)

   class Meta:
       abstract = True

This way you can define your model and extend Basetable to other model class