title: dequeue object from front of queue
body: <p>Am trying to dequeue a random shape from the front of the queue in my tkinter program. I have tried the <code>is_empty()</code> method but I seem to get an error. </p>
  
  <pre><code>&gt;&gt;&gt; AttributeError: 'Queue' object has no attribute 'pop'.
  </code></pre>
  
  <p>Any help would be great thanks !<br>
  This is the queue class I'm using </p>
  
  <pre><code>class Queue:
    def __init__(self):
      self.items = []
    def is_empty(self):
      return self.items == []
    def size(self):
      return len(self.items)
    def enqueue(self, item):
      self.items.insert(0, item)
    def dequeue(self):
      return self.items.pop(0)
    def peek(self):
      return self.items[0]
  </code></pre>
  
  <p>class Recta:</p>
  
  <pre><code>def __init__(self, height=60, width=80 ):
      self.height = height
      self.width = width
      self.create_buttons()
      self.canvas = Canvas(root)
      self.canvas.pack()
      self.queue = Queue()  
  
  
  
  def remove_triangle(self):
      if not self.queue.is_empty(): 
           self.canvas.delete(self.queue.pop())
  </code></pre>