Python: Cannot get attribute from superclass

I know is a pretty basic question, but I've tried for hours and still can't figure it out why I cannot access the attributes of a parent class. My code:

class Queue:
    def __init__(self):
        self.__queue_list = []

    def put(self, val):
        self.__queue_list.insert(0, val)

    def get(self):
        if len(self.__queue_list) == 0:
            raise QueueError
        else:
            val = self.__queue_list[-1]
            del self.__queue_list[-1]
            return val

class SuperQueue(Queue):
    def __init__(self):
        Queue.__init__(self)

    def isempty(self):
        li = Queue.__queue_list
        return bool(len(li))

- when running:

que = SuperQueue()
que.put(1)
que.put("dog")
que.put(False)
for i in range(4):
    if not que.isempty():
        print(que.get())
    else:
        print("Queue empty")

I get the error AttributeError: type object 'Queue' has no attribute '_SuperQueue__queue_list'

I've also tried using super()or in the child class replacing li = Queue.__queue_list with li = self.__queue_list

Nothing works

Solution

The issue here is that you're trying to access the __queue_list attribute directly from the Queue class, which is not allowed since it's a private attribute. Private attributes in Python are "name-mangled" to avoid naming conflicts, which is why you're getting the AttributeError

class Queue:
    def __init__(self):
        self.__queue_list = []

    def put(self, val):
        self.__queue_list.insert(0, val)

    def get(self):
        if len(self.__queue_list) == 0:
            raise QueueError
        else:
            val = self.__queue_list[-1]
            del self.__queue_list[-1]
            return val

class SuperQueue(Queue):
    def __init__(self):
        super().__init__()

    def isempty(self):
        return len(self._Queue__queue_list) == 0

# Usage
que = SuperQueue()
que.put(1)
que.put("dog")
que.put(False)
for i in range(4):
    if not que.isempty():
        print(que.get())
    else:
        print("Queue empty")

Alternately you can use super() also:

def isempty(self):
    return len(super().__queue_list) == 0