def changed ( self ) : return dict ( ( field , self . previous ( field ) ) for field in self . fields if self . has_changed ( field ) )
how to make changed in a dictionary without changing the original python
Returns dict of fields that changed since save ( with old values )
def changed(self):
        """Returns dict of fields that changed since save (with old values)"""
        return dict(
            (field, self.previous(field))
            for field in self.fields
            if self.has_changed(field)
        )