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Python Basic Object-Oriented Python Emulating Built-ins Emulating Built-ins

Posted by DV Shop
DV Shop
1,482 Points

I have tried many times in this exam. But it's not correct. Please, help me.

NameError: name 'Book' is not defined.

book.py 
class Book:
    def __init__(self, author, title):
        self.author = author
        self.title = title
    def __str__(self):
        return f"{self.author}, {self.title}"

    def __eq__(self, other):
        if isinstance(other, Book):
            return self.author == other.author and self.title == other.title
        return False
bookcase.py 
from book import Book


class BookCase:
    def __init__(self):
       self.books = []

    def add_books(self, book):
        self.books.append(book)

1 Answer

Jeff Muday
MOD
Jeff Muday
Treehouse Moderator 28,722 Points
Jeff Muday
Jeff Muday
Treehouse Moderator 28,722 Points

The third part of the challenge tests you understood the yield from keywords and how these relate to the class object __iter__ method.

It's pretty simple. Once you add this method to your object you can pass the challenge.

from book import Book


class BookCase:
    def __init__(self):
       self.books = []

    def add_books(self, book):
        self.books.append(book)

    def __iter__(self):
        yield from self.books

The __iter__ is pretty handy... you can use it to manage looping through your collection .The challenge DOES NOT ask this. But you can put this code to use like this.

book1 = Book('J.D. Salinger', 'The Catcher in the Rye')
book2 = Book('Ayn Rand', 'Atlas Shrugged')
book3 = Book('George Orwell', 'Animal Farm')

mybookcase = BookCase()

mybookcase.add_books(book1)
mybookcase.add_book(book2)
mybookcase.add_book(book3)

for book in mybookcase:
   print(book)

Here is the output:

jeff@pop-os:~/projects/challeges$ python book.py 
J.D. Salinger, The Catcher in the Rye
Ayn Rand, Atlas Shrugged
George Orwell, Animal Farm