title: python set object has not attribute append
body: <p>I am working on a solving a maze with left hand rule and is working on counting on the number of steps taken to solve the maze but I am facing this error:</p>
  <blockquote>
  <p>AttributeError: 'set' object has no attribute 'append'</p>
  </blockquote>
  <p>Portion of the code:</p>
  <pre><code>steps = set()
  def spriteDown(self):
          global steps
          if (self.heading() == 270):                   # checking if pointer is pointing down
              x_walls = round(sprite.xcor(),0)          # pointer x coordinates
              y_walls = round(sprite.ycor(),0)          # pointer y coordinates
              if (x_walls, y_walls) in finish:          # checking if pointer have finished the maze
                  print(&quot;Finished&quot;)
                  endProgram()
              if (x_walls +24, y_walls) in walls:          # checking  if they are walls on the left
                  if(x_walls, y_walls -24) not in walls:   # checking if path ahead is clear
                      self.forward(24)
                      steps = steps.append(1)
                      return steps 
                  else:
                      self.right(90)
                      return steps
  
              else:
                  self.left(90)
                  self.forward(24)
                  return steps 
  </code></pre>