# Superclasses and a useful pattern

# Dog inherits from Animal
class Dog(Animal):
    # When defining the constructor for Dog, you should also run the
    # constructor for Animal by calling super().__init__
    #
    # Using *args and **kwargs allows Animal to change its constructor
    # while your code stays the same.
    def __init__(self, bark_volume, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.bark_volume = bark_volume

# This *args, **kwargs pattern is useful if, for example, you want to
# subclass Thread
from threading import Thread

class SpecializedThread(Thread):
    def __init__(self, special_param, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # do something with special_param

# Now we can pass in arguments we usually give to the Thread constructor,
# like the 'daemon' keyword argument
s = SpecializedThread('special value', daemon=True)