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Python Object-Oriented Python Dice Roller RPG Roller

Andrei Oprescu
Andrei Oprescu
9,547 Points

I don't know what I did wrong

So I have a challenge that asks me to do this:

Now update Hand in hands.py. I'm going to use code similar to Hand.roll(2) and I want to get back an instance of Hand with two D20s rolled in it. I should then be able to call .total on the instance to get the total of the two dice.

I'll leave the implementation of all of that up to you. I don't care how you do it, I only care that it works.

I have done everything that the challenge asked me but I still get an error saying 'Can't get the length of a 'Hand''

My code is at the bottom of the question.

Can someone help me figure it out?


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):
from dice import D20

class Hand(list):
    def __init__(self, die_class=D20):

    def roll(self, size):
        for _ in range(size):

    def total(self):
        return sum(self)         

2 Answers

Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

You are almost there. The following needs to be corrected:

  • Since the access is from class Hand and not an instance of Hand, the method should be decorated with @classmethod. Also, as a classmethod, use cls instead of self in the parameter list to make it clearer.
  • As a classmethod there is no instance to operation on. To create one, use hand = cls()
  • As a classmethod, die_class will not have been passed in or defined. Instead, used D20 directly. Also, remember to append to hand instead of self
  • Lastly, remember to return the object hand

Post back if you need more help. Good luck!!

I also have this error! It keeps saying

Bummer! Can't get the length of a `Hand`

My dice.py is identical to Andrei's. My hands.py is below, it works just fine in the workspace.

import dice

class Hand(list):
    def __init__(self, count=0, diecls=None, *args, **kwargs):
        if not diecls:
            raise ValueError("You must provide a die class")
        if not issubclass(diecls, dice.Die):
            raise TypeError("You must provide a type of die as die class")


        for _ in range(count):

    def roll(cls, count):
        return cls(count=count, diecls=dice.D20)

    def total(self):
        return sum(self) 
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

Comment out the line self.sort. The D20 & Die class does not defined the comparison magic methods needed for sort. Actual error:

Traceback (most recent call last):
  File "<string>", line 3, in <module>
  File "hand.py", line 18, in roll
    return cls(count=count, diecls=dice.D20)
  File "hand.py", line 14, in __init__
TypeError: unorderable types: D20() < D20()

Great! thanks for this tip. My workspace version had the gt and lt magic methods implemented, so that's why it worked there and not in the challenge.

I guess this challenge was meant to work with minimal changes, I found a shorter solution after reading discussions on other questions for this challenge - you can get away with not even overriding Hand class's init!