creating a data structure using another data structure in python

Question

I have a functioning doubly linked list DS that I wrote in python. Using that I want to write queue DS. The specific problem I encounter is in the below.

And I'm not sure whether my way of implementing queue from doubly linked list is correct or not. I googled but didn't find an example of this, in general how do you create a data structure using another data structure in python?

when I run

import import_ipynb
from Queue import *

x=Queue(2)
x.offer(3)

the error it gives me is Queue.__init__() takes from 0 to 1 positional arguments but 2 were given. But I only pass one variable?

This is DoublyLinkedList

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

    def __repr__(self):
        return f"<Node data:{self.data} Previous Node:{self.prev} Next Node:{self.next}>"
    
class DoublyLinkedList:
    def __init__(self):
        self.size=0
        self.head=None
        self.tail=None

    # add an element to the tail of the linked list
    def addL(self,data):
        new_node=Node(data)
        if self.isEmpty()==True:
            self.head=self.tail=new_node
        else:
            self.tail.next=new_node
            new_node.prev=self.tail
            self.tail=new_node
        self.size+=1

This is Queue

import import_ipynb
from DoublyLinkedList import *

class Queue:
    def __init__(firstElem=None):
        list=DoublyLinkedList()
        list.addL(firstElem)

    # add an element to back of the queue
    def offer(val):
        return list.addL(val)

Answer 1

You are forgetting to add the self attribute to the Queue class methods, by default it is the first argument.

Try changing the code to this:

class Queue:
    def __init__(self, firstElem=None):
        self.list=DoublyLinkedList()
        self.list.addL(firstElem)

    # add an element to back of the queue
    def offer(self, val):
        return self.list.addL(val)

Edit: Since you are trying to access the class attribute list from another scope inside the class, you should use it with the self before it, just so you reference the class attribute.