class Element:
    def __init__(self, data, prev, next):
        self.data = data
        self.prev = prev
        self.next = next


class Queue2:
    def __init__(self):
        self.butt = None
        self.head = None

    def isEmpty(self):
        if self.butt is None and self.head is None:
            return True
        else:
            return False

    def showQueue(self):
        print(f"QUEUE head: {self.head}, butt: {self.butt}")
        current = self.head
        while current is not None:
            print(f"Data: {current.data}")
            current = current.next
        print("----")

    def enqueue(self, data):
        newElement = Element(data, self.butt, None)
        self.butt = newElement
        if self.head is None:
            self.head = newElement
        else:
            current = self.head
            while current.next is not None:
                current = current.next
            current.next = newElement

    def dequeue(self):
        if self.head is not None:
            ausgabe = self.head
            self.head = self.head.next
            if self.head is None:
                self.butt = None
            return ausgabe