class client:
    def __init__(self, name, surname):
        self.name = name
        self.surname = surname
        self.borrowedBooks = []

class library:
    def __init__(self):
        self.__clients = []
        self.__books = []

    def addClient(self, client):
        self.__clients.append(client)

    def printClients(self):
        for client in self.__clients:
            print(client.name + ' ' + client.surname)

    def addBook(self, book):
        self.__books.append(book)

    def printBooks(self):
        for book in self.__books:
            print(book.title + ' ' + str(book.code))

    def lend(self, code, client):
        bookToBorrow = self.findBook(code)
        client.borrowedBooks.append(bookToBorrow)

    def findBook(self, code):
        for book in self.__books:
            if code == book.code:
                return book


class book:
    def __init__(self, code, title, authors):
        self.authors = authors
        self.code = code
        self.title = title


class author:
    def __init__(self, name, surname):
        self.name = name
        self.surname = surname


mainLib = library()
client1 = client("Jan", "Kowalski")
mainLib.addClient(client1)
mainLib.printClients()

book1 = book(123, 'Robin Hood', 'Sara B.')
mainLib.addBook(book1)
mainLib.printBooks()
mainLib.lend(123,client1)

print(client1.borrowedBooks[0].title + " is borrowed")