Changes

                       help_string=_('turns the turtle 180 degrees'))

                       help_string=_('turns the turtle 180 degrees'))

    # Next, you need to define what your block will do:

Next, you need to define what your block will do: def_prim takes 3 arguments: the primitive name, the number of arguments—0 in this case—and the function to call—in this case, the canvas.seth function to set the heading.

    # def_prim takes 3 arguments: the primitive name, the number of

 

    # of arguments, 0 in this case, and the function to call, in this

    # case, the canvas function to set the heading.

     self.tw.lc.def_prim('uturn', 0,

     self.tw.lc.def_prim('uturn', 0,

         lambda self: self.tw.canvas.seth(self.tw.canvas.heading + 180))

         lambda self: self.tw.canvas.seth(self.tw.canvas.heading + 180))