Trying to print all nodes as a string in a linked list, however it prints location instead-CodePudding

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

    def getAllBooksInCollection(self):
        node = self.head

Here is the issue below. I amUsing a while loop to print each node, however its printing the location of the node

        while node:
            print(node)
            node = node.next

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 print the nodes of the linked list

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.getAllBooksInCollection())

CodePudding user response：

Fix

As node is a BookCollectionNode, you need to access it's book attribut, then call getBookDetails() method

def getAllBooksInCollection(self):
    node = self.head
    while node:
        print(node.data.getBookDetails())
        node = node.next

Improvements

It seems you don't really need methods to access your properties, but If you really want them, use @property

class Book:
    def __init__(self, title="", author="", year=None):
        self._title = title
        self._author = author
        self._year = year
    @property
    def title(self):
        return self._title
    @property
    def author(self):
        return self._author
    @property
    def year(self):
        return self._year

Override method __str__ to get a builtin string when printing

class BookCollectionNode:
    def __str__(self):
        return str(self.data)

class Book:    
    def __str__(self):
        return f"Title: {self._title}, Author: {self._author}, Year: {self._year}"

For BookCollectionNode getter/setter, the proper way is

class BookCollectionNode:
    def __init__(self, data):
        self._data = data
        self._next = None
    @property
    def data(self):
        return self._data
    @property
    def next(self):
        return self._next
    @data.setter
    def data(self, newData):
        self._data = newData
    @next.setter
    def next(self, newNext):
        self._next = newNext

Finally the BookCollection class becomes

class BookCollection:
    def __init__(self):
        self.head = None
    def insert_book(self, book):
        temp = BookCollectionNode(book)
        temp.next = self.head
        self.head = temp
    # 'print_' and not 'get_' as you don't return anything
    def print_all_books_in_collection(self):
        node = self.head
        while node:
            print(node)
            node = node.next

CodePudding user response：

I think, that you need to add a data argument to your constructor to get something like this:

class Node:

    def __init__(self, data, next=None):
        self.data = data
        self.next = next

# Using an object of a Book with attributes: Title, Author, Year
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)

head = Node(b0, Node(b1, Node(b2, Node(b3))))


def print_list(head, end='\n'):
    while head:
        # You can extend the below logic
        print(head.data, end=' -> ' if head.next else '') 
        head = head.next
    print(end=end)


print_list(head)