trying to use the getBooksByAuthor method to return all the books from that author in the Linked List called BookCollection

Question

Book Object with attributes: Title, Author, Year

class Book():
    def __init__(self, title = "", author = "", year = None):
        self.title = title
        self.author = author
        self.year = year
    def getTitle(self):
        return self.title
    def getAuthor(self):
        return self.author
    def getYear(self):
        return self.year
    def getBookDetails(self):
        string = ("Title: {}, Author: {}, Year: {}"\
                     .format(self.title, self.author, self.year))
        return string

Linked List called BookCollection:

class BookCollection():
    def __init__(self):
        self.head = None
    def insertBook(self, book)
        temp = BookCollectionNode(book)
        temp.setNext(self.head)
        self.head = temp

Trying to return all the books by a certain author

    def getBooksByAuthor(self, author):
        b = Book()
        if author == b.getAuthor():
            return b.getBookDetails

Node class called BookCollectionNode:

class BookCollectionNode():
    def __init__(self, data):
        self.data = data
        self.next = None
    def getData(self):
        return self.data
    def getNext(self):
        return self.next
    def setData(self, newData):
        self.data = newData
    def setNext(self, newNext):
        self.next = newNext

Using the functions below to use the getBooksByAuthorMethod:

b0 = Book("Cujo", "King, Stephen", 1981)
b1 = Book("The Shining", "King, Stephen", 1977)
b2 = Book("Ready Player One", "Cline, Ernest", 2011)
b3 = Book("Rage", "King, Stephen", 1977)
bc = BookCollection()
bc.insertBook(b0)
bc.insertBook(b2)
bc.insertBook(b3)
print(bc.getBooksByAuthor("King, Stephen"))

Trying to get all of Stephen Kings books by using this method. Should return b0, b1, and b3.

Answer 1

There is a problem in getBooksByAuthor. Why do you create a new book in it? Also you don't use self in it which means that you're actually not looking at the books of your collection.

Usually, when you do not use self in a method, it's either because you want your method to return a constant (which can happen) either because you made an error.

So you need to loop on the books of your collection:

    def getBooksByAuthor(self, author):
        node = self.head
        result = list()  # list of book details with the given author
        while node is not None:  # loop on the nodes the collection
            book = node.getData()
            if book.getAuthor() == author:
                result.append(book.getBookDetails())
            node = node.getNext()  # move to the next book of the collection
        return result

Output with the modified getBooksByAuthor (and with adding b1 in your collection, which you forgot):

['Title: Rage, Author: King, Stephen, Year: 1977', 'Title: The Shining, Author: King, Stephen, Year: 1977', 'Title: Cujo, Author: King, Stephen, Year: 1981']