what ' , x ' means in lambda?

it is. But inbuilt iterators are faster than your own loops. Python generators and iterators are written inside interpreter and are much more efficient.

I tested it out.
This Version for long text: 0.0077
Version with my custom loop: 0.0256

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I tried to use intertools in former katas and it seems it's not integred in Codewars and there's no console to install it, heh.

to be clear, this is not the best solution as it uses O(n^2 log n) time; Blind4Basics solution is better.

Best answer

This is the same cheese I did.
I did not vote it as clever because an fstring could be considered a fundamental python feature.
IMO clever code should be the use of obscure stuff so for Python 3 this should be best practice.

nice

...

Never used python2
Thanks !

Because this is Python 2.
In Python 3 you should use next(filter(...)) instead of filter(...)[0] and list(filter(...)) in order to return a list, not a filter object.