class Book:
    def __init__(self, title, author, isbn):
        self.title = title
        self.author = author
        self.isbn = isbn             # isbn means the International Standard Book Number
        self.borrowed = False
        self.published = False
 
    def mark_as_borrowed(self):
        self.borrowed = True
 
    def mark_as_returned(self):
        self.borrowed = False
 
    def __str__(self):
        return f"{self.title} by {self.author} (ISBN: {self.isbn})"
 
 
class Library:
    def __init__(self):
        self.books = []
 
    def add_book(self, book):
        self.books.append(book)
 
    def remove_book(self, isbn):
        self.books = [book for book in self.books if book.isbn != isbn]
 
    def search_by_title(self, title):
        return [book for book in self.books if title.lower() in book.title.lower()]
 
    def search_by_author(self, author):
        return [book for book in self.books if author.lower() in book.author.lower()]
 
    def display_books(self):
        for book in self.books:
            print(book)
 
    def mark_book_as_borrowed(self, isbn):
        for book in self.books:
            if book.isbn == isbn:
                book.mark_as_borrowed()
                break
 
 
def main():
    library = Library()
    while True:
        print("Welcome to my library!")
        print("1. Add Book")
        print("2. Remove Book")
        print("3. Search by Title")
        print("4. Search by Author")
        print("5. Display Books")
        print("6. Mark Book as Borrowed")
        print("7. quit")
        choice = input("Enter your choice: ")
        if choice == "1":
            title = input("enter the title of the book: ")
            author = input("enter the author of the book: ")
            isbn = input("enter the ISBN of the book: ")
            book = Book(title, author, isbn)
            print("Book added successfully")
        elif choice == "2":
            isbn = input("enter the ISBN of the book you want to remove: ")
            library.remove_book(isbn)
            print("Book removed successfully")
        elif choice == "3":
            title = input("enter the title of the book: ")
            result = library.search_by_title(title)
            if result:
                for book in result:
                    print(book)
            else:
                print("Book not found")
        elif choice == "4":
            author = input("enter the author of the book: ")
            result = library.search_by_author(author)
            if result:
                for book in result:
                    print(book)
            else:
                print("Author not found")
        elif choice == "5":
            library.display_books()
        elif choice == "6":
            isbn = input("enter the ISBN of the book to mark as borrowed: ")
            library.mark_book_as_borrowed(isbn)
            print("Book marked as borrowed successfully")
        elif choice == "7":
            print("Thank you for using my library!")
            break
        else:
            print("Invalid choice")
 
 
if __name__ == "__main__":
    main()

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