mine is better

I did this and I thought I was a monster, now I see that there are so many of us :D hahah

I did absolutely the same

explanation please? I note it's a while loop but after the curly brackets, and square brackets it makes less sense

Wow ! I wonder if this solution would come to someone's mind if the tests were not visible.

nice one bro (:

Your codes are very clean

Is it going to look more like one liners in a production environment or will it be more segmented like mine?

It's a horrible idea to use try/except for completely preventable exceptions.

Use spoiler flag if your comment contains info about solution.

Aight, thx for the answers. I'll need to read all that quite a few times and let it cook a little.

You have the correct idea about deep ( or maybe shallow, see above ) copies and mutating the array itself.

Documentation can tell you which methods work by mutation and which by returning a new value.

Mutating input values will mutate it at the called site as well as at the call site, which is dangerous in general and will explicitly fail you in this kata.

Look into the difference between "pure code" and "programming by side effect". Impure code is the source of a lot of very preventable bugs.