38. A touch of class

We have seen how we can add a new method to an existing class, where we wanted to repair the robot so that it knew how to turn right. Here's another example of adding a method to an existing class.

class Amazing(RefurbishedRobot):
    def diag(self):
        self.set_trace_style(1, 'white')
        self.turn_left()
        self.move()
        self.turn_right()
        self.move()
        self.set_trace_style(1, 'sea green')

Magician = Amazing()
Magician.move()
Magician.move()
Magician.diag()
Magician.diag()
Magician.move()
Magician.move()
Magician.turn_off()

The new robot knows all the existing methods that the existing RefurbishedRobot knew [for example, move(), turn_off()] as well as a new one [diag()].

Designing a new class

Sometimes, we want to create a new class that changes the basic behaviour of an existing one. To do so, we need to redefine a special method [__init__()]. The following example is such a case, where we "fix the oil leak", so that the new robot does not leave a trail. Actually, we do more than this as we have it leave a white trail (instead of a sea green one, which is the default), centered on the street or avenue where the robot moves [defined as style number 5] so that it effectively covers the grey dotted line, as though the robot was erasing it.

class Eraser(RefurbishedRobot):
    def __init__(self):
        RefurbishedRobot.__init__(self)
        self.set_trace_style(5, 'white')

Sneaky = Eraser()
while Sneaky.front_is_clear():
    Sneaky.move()
Sneaky.turn_off()

You may want to modify this to try other style numbers (1 to 5) with other colours.

Fixing up Reeborg - - Avoiding repetitions - the important stuff