Called directly after setup, the draw function continuously executes the lines of code contained inside its block until the program is stopped or no_loop is called. The number of times draw executes in each second may be controlled with the frame_rate(xxx).

It is common to call background near the beginning of the draw loop to clear the contents of the window. Since pixels drawn to the window are cumulative, omitting background may result in unintended results, especially when drawing anti-aliased shapes or text.

There can only be one draw function for each sketch, and draw must exist if you want the code to run continuously, or to process events such as mouse_pressed.

def draw
  background 0
  # dynamic code