Basic classes

class User:
    def __init__(self, name, lastname, login, password):
        self.name = name
        self.lastname = lastname
        self.login = login
        self.password = password

    def welcome(self):
        print("Welcome {}{}".format(self.name, self.lastname))

class Admin(User):
    def __init__(self,name="Mateusz", lastname="Grabarczyk", login="admin", password="admin"):
        super().__init__(name, lastname, login, password)

    def welcome(self):
        print("Welcome {} {}, our dear Admin!".format(self.name, self.lastname))


class Student(User):
    def __init__(self, id, name, lastname, login, password):
        super().__init__(name, lastname, login, password)
        self.issued_books = []
        self.id = id
    def welcome(self):
        print("Welcome {} {}, right now you have {} issued books.".format(self.name, self.lastname, len(self.issued_books)))


class UserDatabase():
    student_list = []

    def LoadUsers(self):
        with open("users.txt") as f:
            for line in f:
                data = line.strip().split(',')
                try:
                    student = Student(data[0], data[1], data[2], data[3], data[4])
                    if len(data) > 5:
                        for i in range(5, len(data)):
                            student.issued_books.append(data[i])
                    self.student_list.append(student)
                except:
                    pass

    def overwriteUsersTxt(self):
        with open("users.txt", "w") as f:
            for s in self.student_list:
                f.write("{},{},{},{},{}".format(s.id, s.name, s.lastname, s.login, s.password))
                f.write("\n")

    def print_users(self):
        for user in self.student_list:
            print("{} - {} {}".format(user.id, user.name, user.lastname))