create_bookcase without the classmethod AttributeError

This is how I have done. Although its working magically, not sure how the Bookcase class is using Book class without any inheritance!! Can someone please explain?

class Book:
    def __init__(self, title, author):
        self.title = title
        self.author = author

    def __str__(self):
        return '{} by {}'.format(self.title, self.author)


# ---------------------------------- classmethod(Bookcase) vs self(Bookcase2) ----------------------------- 

class Bookcase:
    def __init__(self, books=None):
        self.books = books

    @classmethod
    def create_bookcase(cls, book_list):
        books = []
        for title, author in book_list:
            books.append(Book(title, author))
        return cls(books)



class Bookcase2():
    def __init__(self):
        self.books = []

    def create_bookcase2(self, book_list):
        for title, author in book_list:
            self.books.append(Book(title, author))
# ---------------------------------------------------xxx-----------------------------------------

Hi Mahbub Aziz, regarding your question: "how the Bookcase class is using Book class without any inheritance!!" you agree with me on the fact that Book & Bookcase are both reside in the same module (book.py). therefore both classes have mutual access in the module code to each class. From the python shell Kenneth has imported the class Bookcase only which naturally has access to the other classes in the same module in case the class Bookcase access them (and as we see it does). and that's totally fine.

Hope this helps.

Mahbub Aziz: The Bookcase consists of multiple Books. Inheriting from it would make sense if every Bookcase is also a Book.

Hi Flore W,

The Exception was raised because you called append on an instance of Bookcase2:

AttributeError: 'Bookcase2' object has no attribute 'append'

which happened on line 29:

File "/home/treehouse/workspace/books.py", line 29, in create_bookcase2

On line 29 inside of create_bookcase2 you call append on self:

for title, author in book_list:
            self.append(Book(title, author))

self is the instance of Bookcase2 not the list. To access the list on self call self.books which has append method.

Correction

for title, author in book_list:
            self.books.append(Book(title, author))