Model fields create with function don't appear in the admin area

Hi Everyone,
My model is working just fine, my only problem is that the field “age” and “id_code” that I create using function don’t appear in my admin area while the other field are there.
What could be the problem? Thank you all

class UserInformation(models.Model): 
    gender_choice = [('m', 'Male'),('f', 'Female')]

    id_code = models.CharField(max_length=120)  
    gender = models.CharField(max_length=120, choices=gender_choice)
    birthdate = models.DateField()
    age = models.CharField(null=True, max_length=2)  
    def __str__(self):
        return self.first_name[:2].lower() + '_' + self.last_name[:2].lower() 

    def age(self):
        age = - int(self.birthdate.year)
        return age

    def id_code(self):
        id_code = self.first_name[:2].lower() + '_' + self.last_name[:2].lower() 
        return id_code

I’m sure it’s because of the naming conflict between the fields you’ve defined and the methods. (It also doesn’t make sense to create an input field for a value that is being generated in a function.)

Thank you! Changing the function name it solved the issue. The field is now visible, but is empty. How could I solve this?

I don’t understand what you’re trying to accomplish here. If this field is a calculated field, there wouldn’t be a field for it in the model.