Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Python Object-Oriented Python Dice Roller Giving a Hand

Don't understand why there I get "TypeError: 'str' object cannot be interpreted as an integer" in my code

from Yatzy import dice

class Hand(list):
    def __init__(self, size=0, die_class=None, *args, **kwargs):
        if not die_class:
            raise ValueError("You must provide a die class!")

        for _ in range(size):

    def __len__(self):
        str_num = str(super().__len__())
        return "There are {} die in this hand".format(str_num)

hand = Hand(size=5, die_class=dice.D6)


When I try to run this code it gives me this error:

TypeError: 'str' object cannot be interpreted as an integer

I've tried analyzing the problem with is instance() for example but I've not come to any conclusions where the problem lies.

I know that print() can take a string as an argument. I also know that if I check the instance of super()__len__() I get back True when I check for an int. If I then do str(super()__len__()) and check what type of instance it is, I get back True for a string and False for an int. When I then return it to be used in print() I get this weird error.

What is happening here?

This is just something extra I wanted to add to keep practicing with overwriting inbuilt methods but I would really like to learn from this.

1 Answer

Steven Parker
Steven Parker
229,005 Points

The override of "__len__" is returning a string message, but the system expects it to return a numeric value.

Did you perhaps intend to override "__str__" instead using this code?

Yes, this was the issue. I didn't realize that the system was expecting a numeric value that had to be filled.

Overriding __str__ with the exact same syntax for the body made it work when using print(hand) and also print(str(hand)) which obviously give the same output.


Steven Parker
Steven Parker
229,005 Points

That's right, because "print" implicitly performs string conversion so you get the same output either way.