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Python Object-Oriented Python Dice Roller RPG Roller

Brad Givens
Brad Givens
6,621 Points
Posted by Brad Givens
Brad Givens
6,621 Points

RPG challenge 2/2. Hands.total not correct value

Keep getting error saying the total value is not correct but I don't see anything that is jumping out at me for being incorrect.

Any thoughts?

dice.py 
import random


class Die:
    def __init__(self, sides=2):
        if sides < 2:
            raise ValueError("Can't have fewer than two sides")
        self.sides = sides
        self.value = random.randint(1, sides)

    def __int__(self):
        return self.value

    def __add__(self, other):
        return int(self) + other

    def __radd__(self, other):
        return self + other

class D20(Die):
    def __init__(self):
        super().__init__(sides=20)
hands.py 
from dice import D20

class Hand(list):
    def __init__(self, dice, *args, **kwargs):
        super().__init__(dice)

    @classmethod
    def roll(cls, num):
        result = []
        for _ in range(num):
            result.append(D20())
        return cls(result)        

    @property
    def total(self):
        return sum(self)

1 Answer

Jay Reyes
seal-mask
.a{fill-rule:evenodd;}techdegree
Jay Reyes
Python Web Development Techdegree Student 15,937 Points
Jay Reyes
.a{fill-rule:evenodd;}techdegree
Jay Reyes
Python Web Development Techdegree Student 15,937 Points

The thing is we don't need to override __init__ -- at least for now.

It turns out, in the scope of the classmethod, we can call cls() (which Kenneth glosses over, I think). Based on this article, cls() will construct class Hand and call the __init__ function.

So the only piece of code you need to add is:

@classmethod
def roll(cls, size=0, die_type=D20):
    hand = cls()
    for _ in range(size):
        hand.append(die_type())
    return hand

The below are just my thoughts: From a high level view, class methods are another way to run the class __init__. I'll now view class methods as template (or constructor).

So it makes sense to name the object hand because we are "stuffing" the class (as an "instance"...) into the class method as a list.

Now, the difference between an instance (not instance method) and a class method? Maybe an instance is the default template while class method is an alternative template.