Calculate AGE in years

[deanhystad]

When you subclass and the superclass has an __init__ method, the subclass needs to call the __init__ method for the superclass. The best way to do that is use super().

class Docent(persoon):
    def __init__(self, naam, sekse, geboortedatum,*Salaris):
        super().__init__(naam, seksa, geboortedatum)
        if(Salaris==None):
            self.Salaris = "0"
        else:
            self.Salaris = Salaris

You are not handling the optional Salaris argument correctly.

class Docent(persoon):
    def __init__(self, naam, sekse, geboortedatum, Salaris=0):
        super().__init__(naam, seksa, geboortedatum)
        self.Salaris = Salaris

Your __init__() method made Python think Solaris was a list of positional arguments following geboortedatum when what you really want is an argument where the user has to option of providing an argument value, or using the default value.