# with inspiration from chapter 21 of The Self-Taught Programmer by Corey Althoff

class Stack:
  """a stack is a LIFO data structure where the last item put in is the first item taken out"""
  def __init__(self):
    self.items = []

  def push(self, item):
    """adds a new item to the stack"""
    return self.items.append(item)

  def pop(self):
    """removes the last item from the stack"""
    return self.items.pop()

  def size(self):
  """returns the size of stack"""
  return len(self.items)


order_ids = [1,2,3,4,5,6,7,8,9]
reversed_order_ids = []
stack = Stack()

for i in order_ids:
  stack.push(i)

for i in range(stack.size()):
  reversed_order_ids.append(stack.pop())

# should return [9,8,7,6,5,4,3,2,1]
print(reversed_order_ids)