Python Object Orientated

Table of Contents

Objects

Creating Instances

>>> class Monster:
...     hit_points=1
...     color="blue"
...     weapon="sword"
...
>>> monster = Monster()
>>> monster.hit_points
1
>>> monster.weapon
'sword'
>>> monster.color
'blue'

# jubjub instance
>>> jubjub = Monster()
>>> type(jubjub)
<type 'instance'>
>>> jubjub.hit_points
1
>>> jubjub.hit_points = 5
>>> jubjub.hit_points
5
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Class Methods

>>> class Methods:
...     a = 2
...     sound="roar"
...     def battlecry(self):
...             return self.sound.upper()
...
>>> general = Methods()
>>> general.battlecry()
'ROAR'
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Code Challenge

class Store:
    open = 9
    close = 18

    def hours(self):
        return "We're open from {} to {}".format(self.open, self.close)
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_ init _

Dealing with the dunder init!

class Monster:
    def __init__(self, **kwargs):
        self.hit_points = kwargs.get('hit_points', 5)
        self.weapon = kwargs.get('weapon', 'sword')
        self.color = kwargs.get('color', 'yellow')
        self.sound = kwargs.get('sound', 'yell')

monster = Monster(hit_points=22, color="green")
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Python Inheritance

Building on from before, we're just making some defaults...

class Monster:
    min_hp = 1
    max_hp = 1
    min_exp = 1
    max_exp = 1
    weapon = 'sword'
    sound = 'roar'

    def __init__(self, **kwargs):
        self.hp = random.randint(self.min_hp, self.max_hp)
        self.exp = random.randint(self.min_exp, self.max_exp)
        self.color = random.choice(COLORS)

        for key, value in kwargs.items():
            setattr(self, key, value)

    def battlecry(self):
        return self.sound.upper()

new_mon = Monster()
new_mon.hp
# 1
new_mon.color
# 'blue'

fresh = Monster(color='blue', sound='whistling', hp='500', adjective='manxsome')
fresh.color
# 'blue'
fresh.adjective
# manxsome
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Python Subclassing

# building on from monster

class Goblin(Monster):
    max_hp = 3
    max_exp = 2
    sound = 'squek'

golbin = Goblin()
goblin.hp
# 2 - now isn't just 1 from the min/max set above!
goblin.color
# 'blue'

class Troll(Monster):
    min_hp = 3
    max_hp = 5
    min_exp = 2
    max_exp = 6
    sound = 'growl'
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Challenge

Create a new class named Dragon that extends the Monster class. Don't forget to import Monster from monster. Give your Dragon an integer size attribute.

from monster import Monster

class Dragon(Monster):
    size = 12
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_ str _

This helps us when we print(object)

class Monster:
    ...
    def __str__(self):
        return '{} {}, HP: {} ...'.format(self.color.title(), self.__class__.__name__, self.hp, self.exp)
    ...

draco = Monster()
print(draco)
# returns the details from the magic method
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Challenge

Import Game from game. Make a new class named GameScore that extends Game. Use pass if needed.

Add a str method to GameScore that returns the score in the string "Player 1: 5; Player 2: 10", using the correct values from self.score. self.score is a tuple with Player 1's score and Player 2's score like (5, 10). You do not need to define self.score. It comes from the Game class.

from game import Game

class GameScore(Game):
    pass

    def __str__(self):
        return "Player 1: {}; Player 2: {}".format(*self.score)
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Instance Methods

class Character:
    exp = 0
    hp = 10

    def __init__(self, **kwargs):
        self.name = input("Name: ")
        self.weapon = self.get_weapon()
        for k, v in kwargs.items():
            setattr(self, k, v)

    def get_weapon(self):
        weapon_choice = input("Weapon: [S]word, [A]xe: ").lower()

        if weapon_choice in 'sa':
            if weapon_choice == 's':
                return 'sword'
            else
                return 'axe'
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Challenge

Add a score method to Game that takes a player argument. The player argument will be either 1 or 2. Increase that player's value in self.current_score by 1. You'll need to adjust the index (i.e. player = 1 means self.current_score[0] needs to increase).

class Game:
  def __init__(self):
    self.current_score = [0, 0]

  def score(self, player):
    if player in [1,2]:
        if player == 1:
            self.current_score[0] += 1
        elif player == 2:
            self.current_score[1] += 1
        return
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Overriding Inheritance

class Character(Combat):
    attack_limit = 10

    # pretend that we're overriding the Combat attack method)
    def attack(self):
        roll = random.randint(1, self.attack_limit)
        if self.weapon == 'sword':
            roll += 1
        elif self.weapon == 'axe':
            roll +=2
        return roll > 4
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Code Challenge

Animal.noise() returns self.sound.lower(). Make Sheep.noise() return the uppercased version of the instance's sound.

from animal import Animal

class Sheep(Animal):
    sound = "Bless"

    def noise(self):
        return self.sound.upper()
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