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Python Object-Oriented Python Dice Roller RPG Roller

sairam poruri
seal-mask
.a{fill-rule:evenodd;}techdegree
sairam poruri
Python Web Development Techdegree Student 3,213 Points
Posted by sairam poruri
.a{fill-rule:evenodd;}techdegree
sairam poruri
Python Web Development Techdegree Student 3,213 Points

Error while creating dice class

Hi,

I get an error while writing the code for the given problem. It says that it can't get the length of the hand but I am inheriting a list which should have inherently have the method present. I have tried creating the len method explicitly too but it did not work.

Please help.

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__(20)
hands.py 
import dice
class Hand(list):
    def __init__(self):
        super().__init__()
    @property
    def total(self):
        return sum(self)

    def roll(self,cont):
        for _ in range(cont):
            self.append(dice.D20())
        return self

1 Answer

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

The instructions say, "I'm going to use code similar to Hand.roll(2) ...". Notice that the method is being called on the class name (Hand) instead of an instance, so this is a clue that "roll" should probably be a class method. And it also said, "I want to get back an instance of Hand..." which is a clue that a new instance should be created by the method and passed back.

sairam poruri
seal-mask
.a{fill-rule:evenodd;}techdegree
sairam poruri
Python Web Development Techdegree Student 3,213 Points
sairam poruri
.a{fill-rule:evenodd;}techdegree
sairam poruri
Python Web Development Techdegree Student 3,213 Points

Hi Steven,

Thank you so much for your help. But I am not able to implement what you said!! Can you point out the mistake that I am making here in this code......

class Hand(list):
    def __init__(self):
        super().__init__()
    @property
    def total(self):
        return sum(self)
    @classmethod
    def roll(klass,cont):
        for _ in range(cont):
            self.append(dice.D20())
        return klass
Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

There's no "self" in a class method, and you still need to create a new instance, append to it, and return it:

    @classmethod
    def roll(klass,cont):
        newhand = klass()               # create a new hand instance
        for _ in range(cont):
            newhand.append(dice.D20())  # append to the new instance
        return newhand                  # return the new instance

Also, you don't need to override "__init__".