class Queue:
def __init__(self):
self._items = LinkedList()
def __iter__(self):
return iter(self._items)
def __len__(self):
return len(self._items)
def __repr__(self):
return repr(self._items)
def enqueue(self, item_to_add):
self._items.append(item_to_add)
def dequeue(self):
result = self.front()
self._items.remove_first()
return result
def front(self):
if len(self._items) == 0:
raise QueueError('empty queue')
return self._items[0]
def __init__(self):
self._items = LinkedList()