Python OOP: Controlling parent class behavior from child class

test.py

"""
Python Object Oriented Programming:
Control Parent Class Behavior from Child Class

Author: Charles Reid
Date: 2018-09-15

This is a short demo of how to conditionally
control the behavior of a parent class from a
child class. This is accomplished by setting 
a class attribute LABEL in the derived class,
and referencing that attribute in the parent
class constructor (where it will be available).

This is a way of dealing with the case where
you have a parent class that performs a task
common to a bunch of child classes, but it
needs information from the child class.
"""

class Parent(object):
    def __init__(self):
        if self.LABEL is None:
            raise Exception("self.LABEL is undefined!")
        if self.LABEL=='red':
            self.red()
        elif self.LABEL=='blue':
            self.blue()

    def red(self):
        print("red fish")
    
    def blue(self):
        print("blue fish")


class RedChild(Parent):
    LABEL = 'red'
    def __init__(self):
        super().__init__()


class BlueChild(Parent):
    LABEL = 'blue'
    def __init__(self):
        super().__init__()


if __name__=="__main__":
    r = RedChild()
    b = BlueChild()

    """
    Outputs:
    red_fish
    blue_fish
    """