(Python) what does the syntax 'slider.var' mean in this function

I am trying to understanding the following codes

s_time = Slider(ax_time, 'Time', 0, 30, valinit=0)


# if deleting the following part, plot will not move
def update(val):
    pos = s_time.val
    ax.axis([pos, pos+10, 20, 40])
    fig.canvas.draw_idle()
s_time.on_changed(update)

I am confused about

What does ‘s_time.val’ here do? a (slider variable).(input parameter)

Thanks!

>Solution :

s_time is an instance of the Slider class. on_changed is an attribute of the Slider class. In your code, there would be code similar to this –

class Slider:
  ...
  def on_changed(self,update):
    update()
  ...

So when you make a new Slider object in a variable called s_time and call the on_changed function, it will reference the code inside the class.