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Python Object-Oriented Python Advanced Objects Frustration

Posted by Michael Russell
Michael Russell
1,575 Points

How would I change the code to include the super() function?

I was able to successfully complete this Python Task Challenge with the following code, but I'm curious as to how I might change it to include the super() function. The instructions say "You'll probably need super() for this," but even with the previous videos/examples of how super() is used, I don't see how/why I could use/need it in this task. Could someone please explain it to me?

frustration.py 
class Liar(list):
    def __init__(self):
        self.slots = []
    def add(self, item):
        self.slots.append(item)
    def __len__(self):
        return len(self.slots) + 2

1 Answer

Michael Hulet
Michael Hulet
47,913 Points
Michael Hulet
Michael Hulet
47,913 Points

The super function is necessary whenever you want to run the original implementation of a method you're overriding from the superclass. In this case, you'll need to call len on super to ensure that the number you return from your implementation of __len__ never matches the actual len from the superclass

For example, you can manipulate an instance of your Liar class to return the same length as its superclass by appending 2 items to it, like this:

example = Liar()

example.append("One")
example.append("Two")

In this case, calling len on example will return 2, which is the right number. This happens because your add function never gets called, so the len of your slots property will be 0. Your implementation of __len__ returns the value of len(self.slots) + 2, and 0 + 2 is 2

The best way to solve this challenge, guaranteeing that it will never return the proper value, would be to apply some arbitrary mathematical operation to another arbitrary number and the value of len(super()). That way, you know the number you definitely can't return, and you're always applying an operation to it in order to guarantee that it changes, and you don't need to override __init__ or define any of your own methods or properties