achievement_models.py

from django.models import Model
from django.auth.models import User

class Achievement(Model):
    user = models.foreignKey(User)
    created_at = models.DateTimeField()


    def fetch_achievement(self):
        #do some achievement logic in here
        pass

    @classmethod
    def get_user_achievements(cls, user):
       #some functionality to fetch achievements for a current user

class SomeAchievement(Achievement):
    achieved = models.BooleanField()
    #achievement specific fields here

    description = "this is the description of the achievement"