How to create a setter in djano models that doesn't mess up the admin or .filter queries!

setter_django.py

class MyModel(models.Model):
    foo = models.CharField(max_length=20)
    bar = models.CharField(max_length=20)

    def __setattr__(self, attrname, val):
        setter_func = 'setter_' + attrname
        if attrname in self.__dict__ and callable(getattr(self, setter_func, None)):
            super(MyModel, self).__setattr__(attrname, getattr(self, setter_func)(val))
        else:
            super(MyModel, self).__setattr__(attrname, val)

    def setter_foo(self, val):
        return val.upper()

"""
Getters and setters are long missing from Django models.
The currently recommended method is to rename fileds with an underscore, and use @property to work as a setter and getter.
But he @property causes problems in admin, and .filter(_foo).  

A better solution would be to override __setattr__ except that this can cause problems initializing the ORM object 
from the DB.  However, there is a trick to get around this, and it's universal.

The secret is '**attrname in self.__dict__**'.  When the model initializes either from new or hydrated 
from the **__dict__**!

"""

buenas tardes, como usar el getattr?

good day, how to use getattr?