Section 20.3 Call a Parent Method
If you compare the code in the __init__ methods of
Point and LabeledPoint, you can see that there is some duplication–the initialization of x and y. We can eliminate the duplication by having LabeledPoint's __init__() method call (execute) Point's __init__() method. That way, each class will be responsible for initializing its own instance variables.All objects keep a reference to the class that created them and every class has a reference to its parent class. You can get an object that represents the parent class using
super() and then call a method on that object.class LabeledPoint(Point):
def __init__(self, initX, initY, label):
super().__init__(initX, initY)
self.label = label
In this example, line 4 invokes the
__init__() method in Point, passing the values of initX and initY to be used in initializing the x and y instance variables.Here is a complete code listing showing both classes, with a version of
__str__() for LabeledPoint that invokes its parent's implementation using super() to avoid duplicating the functionality provided in Point.Finish the code for the
Student class below. In the __init__ method for Student call the __init__ method for Person and pass in a first and last name. Then also set the id. In the __str__ method for Student return the id in the form (id: actual_id,) followed by the string returned from the __str__ method in Person. For example, if s = Student("Abby", "Lane", 1) then print(s) should print “id: 1, name: Abby Lane”.
