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Python Object-Oriented Python Advanced Objects Frustration

Eldin Guzin
Eldin Guzin
6,010 Points
Posted by Eldin Guzin
Eldin Guzin
6,010 Points

Frustration task

Can I get some hints if I am doing this the right way, it gives me a TypeError, that it expects 1 argument but 0 were given.What arguments ? Isn't list the argument that it wants ?? what excatly does len do ? And why do we use super() here, there is no parent class here, so what excatly are we inheriting from? Thanks in advance !

frustration.py 
class Liar(list):
    def __len__(list):
        return super().__len__(list) + 4

1 Answer

Mark Sebeck
MOD
Mark Sebeck
Treehouse Moderator 37,905 Points
Mark Sebeck
Mark Sebeck
Treehouse Moderator 37,905 Points

Don't forget self and don't need any arguments in the return len

class Liar(list):
    def __len__(self):
        return super().__len__() + 4
Timothy Tseng
Timothy Tseng
3,292 Points

Hi Mark, can you explain why we don't need the argument for len? This seems counter intuitive since when len is used "normally" we need to pass the argument through it

Mark Sebeck
Mark Sebeck
Treehouse Moderator 37,905 Points
Mark Sebeck
Mark Sebeck
Treehouse Moderator 37,905 Points

You have to remember that len() is not the same as _ _ len _ _ ()

len() is a function that you use to find the length of an object. len() takes one argument which is the object you want to find the length of.

_ _ len _ _() is a method that the len() function uses. _ _ len _ _ () is being used behind the scenes by Python. It does't take any parameters. Here it is a method of the list class. You use it like: [list]. _ _ len _ _ ().

Here is a explanation I found on stack overflow.

https://stackoverflow.com/questions/2481421/difference-between-len-and-len

Hope this helps.