Exercise: Inheritance
These exercises are all about overriding base classes. In the first two exercises, you'll override just the class variables. In the last two, you'll also override methods.
Exercise: Animal Subclasses
Finish the two subclasses Sloth and Cat so that they both inherit from Animal and override class variables according to the values in their doctests.
📺 Need help with this one? Watch this video walkthrough of a partial solution. Then try it out yourself and apply what you learned to the next exercise.
class Animal:
species_name = "Animal"
scientific_name = "Animalia"
play_multiplier = 2
interact_increment = 1
def __init__(self, name, age=0):
self.name = name
self.age = age
self.calories_eaten = 0
self.happiness = 0
def play(self, num_hours):
self.happiness += (num_hours * self.play_multiplier)
print("WHEEE PLAY TIME!")
def eat(self, food):
self.calories_eaten += food.calories
print(f"Om nom nom yummy {food.name}")
if self.calories_eaten > self.calories_needed:
self.happiness -= 1
print("Ugh so full")
def interact_with(self, animal2):
self.happiness += self.interact_increment
print(f"Yay happy fun time with {animal2.name}")
class Sloth: # <- FINISH THIS LINE
"""
>>> Sloth.species_name
"Hoffmann's two-toed sloth"
>>> Sloth.scientific_name
'Choloepus hoffmanni'
>>> Sloth.calories_needed
680
>>> buttercup = Sloth('Buttercup', 27)
>>> buttercup.name
'Buttercup'
>>> buttercup.age
27
"""
# YOUR CODE HERE
class Cat: # <- FINISH THIS LINE
"""
>>> Cat.species_name
'Domestic cat'
>>> Cat.scientific_name
'Felis silvestris catus'
>>> Cat.calories_needed
200
>>> jackson = Cat("Jackson", 8)
>>> jackson.name
'Jackson'
>>> jackson.age
8
"""
# YOUR CODE HERE
Exercise: LearnableContent subclasses
The LearnableContent class below is based on an actual class from the Khan Academy Python codebase. Finish the implementation of the Article and Video subclasses to properly inherit from LearnableContent and override class variables according to the values in the doctests.
class LearnableContent:
"""A base class for specific kinds of learnable content.
All kinds have title and author attributes,
but each kind may have additional attributes.
"""
license = "Creative Commons"
def __init__(self, title, author):
self.title = title
self.author = author
def get_heading(self):
return f"{self.title} by {self.author}"
class Video: # <- FINISH THIS LINE
"""
>>> Video.license
'YouTube Standard License'
>>> dna_vid = Video('DNA', 'Megan')
>>> dna_vid.title
'DNA'
>>> dna_vid.author
'Megan'
>>> dna_vid.get_heading()
'DNA by Megan'
"""
# YOUR CODE HERE
class Article: # <- FINISH THIS LINE
"""
>>> Article.license
'CC-BY-NC-SA'
>>> water_article = Article('Water phases', 'Lauren')
>>> water_article.title
'Water phases'
>>> water_article.author
'Lauren'
>>> water_article.get_heading()
'Water phases by Lauren'
"""
# YOUR CODE HERE
Exercise: Boss methods
The Character class below represents a character in a video game. Finish implementing the methods in Boss so that they override the base class methods and behave according to the comments and doctests.
📺 Need help with this one? Watch this video walkthrough of a partial solution. Then try it out yourself and apply what you learned to the next exercise.
class Character:
""" Represents a character in a video game,
tracking their name and health.
>>> player = Character("Mario")
>>> player.name
'Mario'
>>> player.health
100
>>> player.damage(10)
>>> player.health
90
>>> player.boost(5)
>>> player.health
95
"""
def __init__(self, name):
self.name = name
self.health = 100
def damage(self, amount):
self.health -= amount
def boost(self, amount):
self.health += amount
class Boss(Character):
""" Tracks a Boss character in a video game.
>>> mx_boss = Boss("Mx Boss Person")
>>> mx_boss.damage(100)
>>> mx_boss.health
99
>>> mx_boss.damage(10)
>>> mx_boss.health
98
>>> mx_boss.boost(1)
>>> mx_boss.health
100
"""
def damage(self, amount):
# Bosses ignore the amount and instead
# always receive 1 unit of damage to their health
# YOUR CODE HERE
def boost(self, amount):
# Bosses always receive twice the amount of boost to their health
# YOUR CODE HERE
Exercise: Clothing methods
The Clothing class below represents pieces of clothing in a closet, and KidsClothing inherits from it. Write a clean method that overrides the base class method according to the comment and the doctests.
class Clothing:
""" Represents clothing in a closet,
tracking the color, category, and clean/dirty state.
>>> blue_shirt = Clothing("shirt", "blue")
>>> blue_shirt.category
'shirt'
>>> blue_shirt.color
'blue'
>>> blue_shirt.is_clean
True
>>> blue_shirt.wear()
>>> blue_shirt.is_clean
False
>>> blue_shirt.clean()
>>> blue_shirt.is_clean
True
"""
def __init__(self, category, color):
self.category = category
self.color = color
self.is_clean = True
def wear(self):
self.is_clean = False
def clean(self):
self.is_clean = True
class KidsClothing(Clothing):
"""
>>> onesie = KidsClothing("onesie", "polka dots")
>>> onesie.wear()
>>> onesie.is_clean
False
>>> onesie.clean()
>>> onesie.is_clean
False
>>> dress = KidsClothing("dress", "rainbow")
>>> dress.clean()
>>> dress.is_clean
True
>>> dress.wear()
>>> dress.is_clean
False
>>> dress.clean()
>>> dress.is_clean
False
"""
# Override the clean() method
# so that kids clothing always stays dirty!
# YOUR CODE HERE