That’s not something you do as a field. Even if that syntax worked, it would only give the value when the class was defined, not at the time you access it. You should do this as a method, and you can use the @property
decorator to make it look like a normal attribute.
@property
def name(self):
return ''.join(
[self.lastname,' ,', self.firstname, ' ', self.middlename])
self.lastname
etc appear as just their values, so no need to call any other method to convert them.