Python class exmaple

import datetime

class Company:
    def __init__(self, name, founded):
        self.name = name              # свойство, поле  property, field
        self.name_in_capital = name.upper()
        self.founded = founded

    def age(self):
        return datetime.datetime.now().year - self.founded

    def older(self, other):
        return self.founded < other.founded

    def __lt__(self, other):
        return self.older(other)

    def __eq__(self, other):
        return self.founded <= other.founded

    def __str__(self):
        return 'Company <<' + self.name + '>>'

class StockCompany(Company):
    def __init__(self, name, founded, stockholders):
        super().__init__(name, founded)
        self.stockholders = stockholders[-2:]

    def __str__(self):
        #return 'Stock Company "' + self.name + '"' # override
        return 'Stock ' + super().__str__()

c = Company("Напрасный труд", 2019)
s = ["a", "b"]
d = StockCompany("True", 2019, s)
print(d.stockholders)
s.append("c")
print(d.stockholders)