def pop(self):
""" Remove and return the element at the top of the stack"""
if self.is_empty():
raise Empty('Stack if empty')
pop_value = self._head._element
self._head = self._head._next
self._size -= 1
return pop_value
def dequeue(self):
""" Remove and return the first element of the queue"""
if self.is_empty():
raise Empty('Stack if empty')
first_value = self._head._element
self._head = self._head._next
self._size -= 1
if self.is_empty():
self._tail = None
return first_value
def dequeue(self):
""" Remove and return the first element at the queue"""
if self.is_empty():
raise Empty('Queue is empty')
head = self._tail._next
if self._size == 1:
self._tail = None
else:
self._tail._next = head._next
self._size -= 1
return head._element
def first(self):
""" Return but not remove the first element at the queue"""
if self.is_empty():
raise Empty('Queue is empty')
head = self._tail._next
return head._element
def top(self):
""" Return but not remove the element at the top of the stack"""
if self.is_empty():
raise Empty('Stack if empty')
return self._head._element
def delete_last(self):
if self.is_empty():
raise Empty(' Deque is empty')
return self._delete_node(self._trailer._prev)
def delete_first(self):
if self.is_empty():
raise Empty(' Deque is empty')
return self._delete_node(self._header._next)
def last(self):
if self.is_empty():
raise Empty('Deque is empty')
return self._trailer._prev._element
def first(self):
if self.is_empty():
raise Empty('Deque is empty')
return self._header._next._element