Class Inheritance, using Child Class to set up Parent Class

Question

I am trying to learn a little more about Classes in Python, and am writing a program to help with this. I have defined my Parent Class and Child class as follows:

class Character():
'Common base class for all characters'
    def __init__(self):
        self.attack = 1
        self.defence = 1
        self.strength = 1

    def setAttack(self, attack):
        self.attack = attack

    def setDefence(self, defence):
        self.defence = defence

    def setStrength(self, strength):
        self.strength = strength

class Enemy(Character):
    'Enemy Class'
    def __init__(self):
        self.setAttack(random.randint(5,20))
        self.setDefence(random.randint(5,20))
        self.setStrength(random.randint(5,20))

This means I can define an enemy with the line

enemy1 = Enemy()

My view is I can then copy the Enemy class with different random values to create different types of enemy. i.e. Create a BiggerEnemy Class the same as above but with different random values.

While this code above works, all the text books and documentation I have read indicate I should structure my code as such:

class Character():
    'Common base class for all characters'
    def __init__(self, attack, defence, strength):
        self.attack = attack
        self.defence = defence
        self.strength = strength

    def setAttack(self, attack):
        self.attack = attack

    def setDefence(self, defence):
        self.defence = defence

    def setStrength(self, strength):
        self.strength = strength


class Enemy(Character):
    'Enemy Class'
    def __init__(self, attack,defence,strength):
        Character.__init__(self, attack, defence, strength)
        self.attack = attack
        self.defence = defence
        self.strength = strength
        self.setAttack(random.randint(5,20))
        self.setDefence(random.randint(5,20))
        self.setStrength(random.randint(5,20))

Which is fine, but this means I would have to declare what goes into the Child class by setting Attack, Defence and Strength in order to create the enemy

enemy1 = Enemy(10,10,10)

I am wondering if my method is incorrect, and if I am missing something about how classes work. All the documentation I have read seems to point to the fact I am wrong with my code, but the alternative seems to negate the need for the Child Class. Hence my first posting on stackoverflow.

So do you want random values for attack/defense/strength? Or the inputs? — Dan Oberlam
– Dan Oberlam, Commented Nov 20, 2014 at 21:46

Daniel · Accepted Answer · 2014-11-20 21:53:27Z

2

It's good practice to call the super-init-method, so I would suggest:

class Character():
    'Common base class for all characters'
    def __init__(self, attack, defence, strength):
        self.attack = attack
        self.defence = defence
        self.strength = strength


class Enemy(Character):
    'Enemy Class'
    def __init__(self):
        Character.__init__(self, attack=random.randint(5,20),
            defence=random.randint(5,20), strength=random.randint(5,20))

The setters are unnecessary.

answered Nov 20, 2014 at 21:53

Daniel

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1 Comment

Trevor Appleton Over a year ago

Daniel, That looks really good! Thanks, I have been struggling to work out the correct way to implement this. Many thanks.

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