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Python Object-Oriented Python Advanced Objects Frustration

James J. McCombie
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James J. McCombie
Python Web Development Techdegree Graduate 21,199 Points
Posted by James J. McCombie
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James J. McCombie
Python Web Development Techdegree Graduate 21,199 Points

liar __len__

Hello, the course is Object-Orientated-Python, the section is Advanced-Objects, and the challenge is titled Frustration (aptly!). With the code below:

import random

class Liar(list):
    def __len__(self):
        return super().__len__() * random.randint(1, 100)

I get the error message 'Bummer! Didn't get the wrong len for a Liar instance'.

It consistantly generates the wrong length of an instance of Liar when run locally.

Any help appreciated

James

James J. McCombie
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.a{fill-rule:evenodd;}techdegree seal-36
James J. McCombie
Python Web Development Techdegree Graduate 21,199 Points
James J. McCombie
.a{fill-rule:evenodd;}techdegree seal-36
James J. McCombie
Python Web Development Techdegree Graduate 21,199 Points

ok, so in the instructions, it stated that for example a list of 5 objects, would be reported by the liar class as having 2, or 8 objects, so it would seem that the challenge expects a specific lie, namely 3 more or less than present, since negative lengths seem inappropriate for most cases, I added a check to make sure this would not be the case. This now passes. 

class Liar(list):
    def __len__(self):
        true_length = super().__len__()
        if true_length - 3 < 0:
            return true_length + 3
        else:
            return true_length + random.choice([3, -3])

1 Answer

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

It doesn't have to be random.

I'm not sure why, but this seems to be a common misinterpretation of this challenge. And the amount of offset is also not important, so any positive value will do.

James J. McCombie
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
James J. McCombie
Python Web Development Techdegree Graduate 21,199 Points
James J. McCombie
.a{fill-rule:evenodd;}techdegree seal-36
James J. McCombie
Python Web Development Techdegree Graduate 21,199 Points

Hello Steven,

The challenge requires a wrong result when len is called on a class instance, it does not actually state anything beyond that in terms of requirements. It states an example, a list of 5 could be 8 or 2, it does not state it is expecting anything wrong in particular, so it comes as no surprise it is a 'common misinterpreation'

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

The instructions could be a bit clearer. And they could warn you that negative values won't be accepted.

You might want to submit a bug report using the Support page.